diff --git a/apps/web/src/locales/en/messages.json b/apps/web/src/locales/en/messages.json
index 34551f68cc0..6cf04fee7f2 100644
--- a/apps/web/src/locales/en/messages.json
+++ b/apps/web/src/locales/en/messages.json
@@ -10346,5 +10346,32 @@
         "example": "10"
       }
     }
+  },
+  "existingOrganization": {
+    "message": "Existing organization"
+  },
+  "selectOrganizationProviderPortal": {
+    "message": "Select an organization to add to your Provider Portal."
+  },
+  "noOrganizations": {
+    "message": "There are no organizations to list"
+  },
+  "yourProviderSubscriptionCredit": {
+    "message": "Your provider subscription will receive a credit for any remaining time in the organization's subscription."
+  },
+  "doYouWantToAddThisOrg": {
+    "message": "Do you want to add this organization to $PROVIDER$?",
+    "placeholders": {
+      "provider": {
+        "content": "$1",
+        "example": "Cool MSP"
+      }
+    }
+  },
+  "addedExistingOrganization": {
+    "message": "Added existing organization"
+  },
+  "assignedExceedsAvailable": {
+    "message": "Assigned seats exceed available seats."
   }
 }
diff --git a/bitwarden_license/bit-web/src/app/admin-console/providers/providers.module.ts b/bitwarden_license/bit-web/src/app/admin-console/providers/providers.module.ts
index 37cb9618b60..3310be7ba36 100644
--- a/bitwarden_license/bit-web/src/app/admin-console/providers/providers.module.ts
+++ b/bitwarden_license/bit-web/src/app/admin-console/providers/providers.module.ts
@@ -17,6 +17,7 @@ import {
   ProviderSubscriptionComponent,
   ProviderSubscriptionStatusComponent,
 } from "../../billing/providers";
+import { AddExistingOrganizationDialogComponent } from "../../billing/providers/clients/add-existing-organization-dialog.component";
 
 import { AddOrganizationComponent } from "./clients/add-organization.component";
 import { CreateOrganizationComponent } from "./clients/create-organization.component";
@@ -63,6 +64,7 @@ import { VerifyRecoverDeleteProviderComponent } from "./verify-recover-delete-pr
     SetupProviderComponent,
     UserAddEditComponent,
     AddEditMemberDialogComponent,
+    AddExistingOrganizationDialogComponent,
     CreateClientDialogComponent,
     ManageClientNameDialogComponent,
     ManageClientSubscriptionDialogComponent,
diff --git a/bitwarden_license/bit-web/src/app/admin-console/providers/services/web-provider.service.ts b/bitwarden_license/bit-web/src/app/admin-console/providers/services/web-provider.service.ts
index 264b43aee9d..6b9765e9e05 100644
--- a/bitwarden_license/bit-web/src/app/admin-console/providers/services/web-provider.service.ts
+++ b/bitwarden_license/bit-web/src/app/admin-console/providers/services/web-provider.service.ts
@@ -1,8 +1,11 @@
 // FIXME: Update this file to be type safe and remove this and next line
 // @ts-strict-ignore
 import { Injectable } from "@angular/core";
+import { firstValueFrom, map } from "rxjs";
+import { switchMap } from "rxjs/operators";
 
 import { ApiService } from "@bitwarden/common/abstractions/api.service";
+import { ProviderApiServiceAbstraction } from "@bitwarden/common/admin-console/abstractions/provider/provider-api.service.abstraction";
 import { OrganizationKeysRequest } from "@bitwarden/common/admin-console/models/request/organization-keys.request";
 import { ProviderAddOrganizationRequest } from "@bitwarden/common/admin-console/models/request/provider/provider-add-organization.request";
 import { BillingApiServiceAbstraction } from "@bitwarden/common/billing/abstractions/billing-api.service.abstraction";
@@ -10,6 +13,8 @@ import { PlanType } from "@bitwarden/common/billing/enums";
 import { CreateClientOrganizationRequest } from "@bitwarden/common/billing/models/request/create-client-organization.request";
 import { EncryptService } from "@bitwarden/common/platform/abstractions/encrypt.service";
 import { I18nService } from "@bitwarden/common/platform/abstractions/i18n.service";
+import { StateProvider } from "@bitwarden/common/platform/state";
+import { OrganizationId } from "@bitwarden/common/types/guid";
 import { OrgKey } from "@bitwarden/common/types/key";
 import { SyncService } from "@bitwarden/common/vault/abstractions/sync/sync.service.abstraction";
 import { KeyService } from "@bitwarden/key-management";
@@ -23,6 +28,8 @@ export class WebProviderService {
     private i18nService: I18nService,
     private encryptService: EncryptService,
     private billingApiService: BillingApiServiceAbstraction,
+    private stateProvider: StateProvider,
+    private providerApiService: ProviderApiServiceAbstraction,
   ) {}
 
   async addOrganizationToProvider(providerId: string, organizationId: string) {
@@ -40,6 +47,22 @@ export class WebProviderService {
     return response;
   }
 
+  async addOrganizationToProviderVNext(providerId: string, organizationId: string): Promise<void> {
+    const orgKey = await firstValueFrom(
+      this.stateProvider.activeUserId$.pipe(
+        switchMap((userId) => this.keyService.orgKeys$(userId)),
+        map((organizationKeysById) => organizationKeysById[organizationId as OrganizationId]),
+      ),
+    );
+    const providerKey = await this.keyService.getProviderKey(providerId);
+    const encryptedOrgKey = await this.encryptService.encrypt(orgKey.key, providerKey);
+    await this.providerApiService.addOrganizationToProvider(providerId, {
+      key: encryptedOrgKey.encryptedString,
+      organizationId,
+    });
+    await this.syncService.fullSync(true);
+  }
+
   async createClientOrganization(
     providerId: string,
     name: string,
diff --git a/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.html b/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.html
new file mode 100644
index 00000000000..a22484ed92d
--- /dev/null
+++ b/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.html
@@ -0,0 +1,73 @@
+<bit-dialog [loading]="loading">
+  <span bitDialogTitle>
+    {{ "addExistingOrganization" | i18n }}
+  </span>
+  <ng-container bitDialogContent>
+    <ng-container *ngIf="!selectedOrganization; else organizationSelected">
+      <p>{{ "selectOrganizationProviderPortal" | i18n }}</p>
+      <bit-table>
+        <ng-container header>
+          <tr>
+            <th colspan="2" bitCell>{{ "name" | i18n }}</th>
+            <th bitCell>{{ "assigned" | i18n }}</th>
+          </tr>
+        </ng-container>
+        <ng-template body>
+          <tr
+            bitRow
+            *ngFor="let addable of addableOrganizations"
+            [ngClass]="{ 'tw-text-muted': addable.disabled }"
+          >
+            <td bitCell class="tw-w-8">
+              <bit-avatar [text]="addable.name" [id]="addable.id" size="small"></bit-avatar>
+            </td>
+            <td bitCell>
+              {{ addable.name }}
+              <div *ngIf="addable.disabled" class="tw-text-xs">
+                {{ "assignedExceedsAvailable" | i18n }}
+              </div>
+            </td>
+            <td bitCell>{{ addable.seats }}</td>
+            <td bitCell class="tw-text-right">
+              <button
+                type="button"
+                bitButton
+                buttonType="secondary"
+                [disabled]="addable.disabled"
+                (click)="selectOrganization(addable.id)"
+              >
+                {{ "next" | i18n }}
+              </button>
+            </td>
+          </tr>
+        </ng-template>
+      </bit-table>
+      <p *ngIf="addableOrganizations.length === 0" class="tw-text-muted tw-mt-2">
+        {{ "noOrganizations" | i18n }}
+      </p>
+    </ng-container>
+    <ng-template #organizationSelected>
+      <p>{{ "yourProviderSubscriptionCredit" | i18n }}</p>
+      <p>{{ "doYouWantToAddThisOrg" | i18n: dialogParams.provider.name }}</p>
+      <div class="tw-flex tw-flex-col">
+        <div>{{ "organization" | i18n }}: {{ selectedOrganization.name }}</div>
+        <div>{{ "billingPlan" | i18n }}: {{ selectedOrganization.plan }}</div>
+        <div>{{ "assignedSeats" | i18n }}: {{ selectedOrganization.seats }}</div>
+      </div>
+    </ng-template>
+  </ng-container>
+  <ng-container bitDialogFooter>
+    <button
+      *ngIf="selectedOrganization"
+      type="button"
+      bitButton
+      buttonType="primary"
+      [bitAction]="addExistingOrganization"
+    >
+      {{ "addOrganization" | i18n }}
+    </button>
+    <button bitButton buttonType="secondary" type="button" [bitDialogClose]="ResultType.Closed">
+      {{ "close" | i18n }}
+    </button>
+  </ng-container>
+</bit-dialog>
diff --git a/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.ts b/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.ts
new file mode 100644
index 00000000000..3df0693d091
--- /dev/null
+++ b/bitwarden_license/bit-web/src/app/billing/providers/clients/add-existing-organization-dialog.component.ts
@@ -0,0 +1,82 @@
+import { DIALOG_DATA, DialogConfig, DialogRef } from "@angular/cdk/dialog";
+import { Component, Inject, OnInit } from "@angular/core";
+
+import { ProviderApiServiceAbstraction } from "@bitwarden/common/admin-console/abstractions/provider/provider-api.service.abstraction";
+import { Provider } from "@bitwarden/common/admin-console/models/domain/provider";
+import { AddableOrganizationResponse } from "@bitwarden/common/admin-console/models/response/addable-organization.response";
+import { I18nService } from "@bitwarden/common/platform/abstractions/i18n.service";
+import { DialogService, ToastService } from "@bitwarden/components";
+
+import { WebProviderService } from "../../../admin-console/providers/services/web-provider.service";
+
+export type AddExistingOrganizationDialogParams = {
+  provider: Provider;
+};
+
+export enum AddExistingOrganizationDialogResultType {
+  Closed = "closed",
+  Submitted = "submitted",
+}
+
+@Component({
+  templateUrl: "./add-existing-organization-dialog.component.html",
+})
+export class AddExistingOrganizationDialogComponent implements OnInit {
+  protected loading: boolean = true;
+
+  addableOrganizations: AddableOrganizationResponse[] = [];
+  selectedOrganization?: AddableOrganizationResponse;
+
+  protected readonly ResultType = AddExistingOrganizationDialogResultType;
+
+  constructor(
+    @Inject(DIALOG_DATA) protected dialogParams: AddExistingOrganizationDialogParams,
+    private dialogRef: DialogRef<AddExistingOrganizationDialogResultType>,
+    private i18nService: I18nService,
+    private providerApiService: ProviderApiServiceAbstraction,
+    private toastService: ToastService,
+    private webProviderService: WebProviderService,
+  ) {}
+
+  async ngOnInit() {
+    this.addableOrganizations = await this.providerApiService.getProviderAddableOrganizations(
+      this.dialogParams.provider.id,
+    );
+    this.loading = false;
+  }
+
+  addExistingOrganization = async (): Promise<void> => {
+    if (this.selectedOrganization) {
+      await this.webProviderService.addOrganizationToProviderVNext(
+        this.dialogParams.provider.id,
+        this.selectedOrganization.id,
+      );
+
+      this.toastService.showToast({
+        variant: "success",
+        title: "",
+        message: this.i18nService.t("addedExistingOrganization"),
+      });
+
+      this.dialogRef.close(this.ResultType.Submitted);
+    }
+  };
+
+  selectOrganization(organizationId: string) {
+    this.selectedOrganization = this.addableOrganizations.find(
+      (organization) => organization.id === organizationId,
+    );
+  }
+
+  static open = (
+    dialogService: DialogService,
+    dialogConfig: DialogConfig<
+      AddExistingOrganizationDialogParams,
+      DialogRef<AddExistingOrganizationDialogResultType>
+    >,
+  ) =>
+    dialogService.open<
+      AddExistingOrganizationDialogResultType,
+      AddExistingOrganizationDialogParams
+    >(AddExistingOrganizationDialogComponent, dialogConfig);
+}
diff --git a/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.html b/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.html
index 7c560e49579..077aeb6c124 100644
--- a/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.html
+++ b/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.html
@@ -1,9 +1,39 @@
 <app-header>
   <bit-search [placeholder]="'search' | i18n" [formControl]="searchControl"></bit-search>
-  <a type="button" bitButton *ngIf="isProviderAdmin" buttonType="primary" (click)="createClient()">
-    <i class="bwi bwi-plus bwi-fw" aria-hidden="true"></i>
-    {{ "addNewOrganization" | i18n }}
-  </a>
+  <ng-container *ngIf="addExistingOrgsFromProviderPortal$ | async; else addExistingOrgsDisabled">
+    <button
+      bitButton
+      buttonType="primary"
+      type="button"
+      [bitMenuTriggerFor]="clientMenu"
+      appA11yTitle="{{ 'add' | i18n }}"
+    >
+      <i class="bwi bwi-plus bwi-fw" aria-hidden="true"></i>
+      {{ "add" | i18n }}
+    </button>
+    <bit-menu #clientMenu>
+      <button type="button" bitMenuItem (click)="createClient()">
+        <i aria-hidden="true" class="bwi bwi-business"></i>
+        {{ "newClient" | i18n }}
+      </button>
+      <button type="button" bitMenuItem (click)="addExistingOrganization()">
+        <i aria-hidden="true" class="bwi bwi-sitemap"></i>
+        {{ "existingOrganization" | i18n }}
+      </button>
+    </bit-menu>
+  </ng-container>
+  <ng-template #addExistingOrgsDisabled>
+    <a
+      type="button"
+      bitButton
+      *ngIf="isProviderAdmin"
+      buttonType="primary"
+      (click)="createClient()"
+    >
+      <i class="bwi bwi-plus bwi-fw" aria-hidden="true"></i>
+      {{ "addNewOrganization" | i18n }}
+    </a>
+  </ng-template>
 </app-header>
 
 <ng-container *ngIf="loading">
diff --git a/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.ts b/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.ts
index ee2c541e72f..07434369122 100644
--- a/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.ts
+++ b/bitwarden_license/bit-web/src/app/billing/providers/clients/manage-clients.component.ts
@@ -11,6 +11,8 @@ import { Provider } from "@bitwarden/common/admin-console/models/domain/provider
 import { ProviderOrganizationOrganizationDetailsResponse } from "@bitwarden/common/admin-console/models/response/provider/provider-organization.response";
 import { BillingApiServiceAbstraction } from "@bitwarden/common/billing/abstractions";
 import { PlanResponse } from "@bitwarden/common/billing/models/response/plan.response";
+import { FeatureFlag } from "@bitwarden/common/enums/feature-flag.enum";
+import { ConfigService } from "@bitwarden/common/platform/abstractions/config/config.service";
 import { I18nService } from "@bitwarden/common/platform/abstractions/i18n.service";
 import { ValidationService } from "@bitwarden/common/platform/abstractions/validation.service";
 import {
@@ -25,6 +27,10 @@ import { HeaderModule } from "@bitwarden/web-vault/app/layouts/header/header.mod
 
 import { WebProviderService } from "../../../admin-console/providers/services/web-provider.service";
 
+import {
+  AddExistingOrganizationDialogComponent,
+  AddExistingOrganizationDialogResultType,
+} from "./add-existing-organization-dialog.component";
 import {
   CreateClientDialogResultType,
   openCreateClientDialog,
@@ -62,6 +68,9 @@ export class ManageClientsComponent {
 
   protected searchControl = new FormControl("", { nonNullable: true });
   protected plans: PlanResponse[] = [];
+  protected addExistingOrgsFromProviderPortal$ = this.configService.getFeatureFlag$(
+    FeatureFlag.PM15179_AddExistingOrgsFromProviderPortal,
+  );
 
   constructor(
     private billingApiService: BillingApiServiceAbstraction,
@@ -73,6 +82,7 @@ export class ManageClientsComponent {
     private toastService: ToastService,
     private validationService: ValidationService,
     private webProviderService: WebProviderService,
+    private configService: ConfigService,
   ) {
     this.activatedRoute.queryParams.pipe(first(), takeUntilDestroyed()).subscribe((queryParams) => {
       this.searchControl.setValue(queryParams.search);
@@ -111,19 +121,30 @@ export class ManageClientsComponent {
 
   async load() {
     this.provider = await firstValueFrom(this.providerService.get$(this.providerId));
-
     this.isProviderAdmin = this.provider?.type === ProviderUserType.ProviderAdmin;
-
-    const clients = (await this.billingApiService.getProviderClientOrganizations(this.providerId))
-      .data;
-
-    this.dataSource.data = clients;
-
+    this.dataSource.data = (
+      await this.billingApiService.getProviderClientOrganizations(this.providerId)
+    ).data;
     this.plans = (await this.billingApiService.getPlans()).data;
-
     this.loading = false;
   }
 
+  addExistingOrganization = async () => {
+    if (this.provider) {
+      const reference = AddExistingOrganizationDialogComponent.open(this.dialogService, {
+        data: {
+          provider: this.provider,
+        },
+      });
+
+      const result = await lastValueFrom(reference.closed);
+
+      if (result === AddExistingOrganizationDialogResultType.Submitted) {
+        await this.load();
+      }
+    }
+  };
+
   createClient = async () => {
     const reference = openCreateClientDialog(this.dialogService, {
       data: {
diff --git a/libs/common/src/admin-console/abstractions/provider/provider-api.service.abstraction.ts b/libs/common/src/admin-console/abstractions/provider/provider-api.service.abstraction.ts
index f348e7487de..ffe79f0ad3b 100644
--- a/libs/common/src/admin-console/abstractions/provider/provider-api.service.abstraction.ts
+++ b/libs/common/src/admin-console/abstractions/provider/provider-api.service.abstraction.ts
@@ -1,5 +1,7 @@
 // FIXME: Update this file to be type safe and remove this and next line
 // @ts-strict-ignore
+import { AddableOrganizationResponse } from "@bitwarden/common/admin-console/models/response/addable-organization.response";
+
 import { ProviderSetupRequest } from "../../models/request/provider/provider-setup.request";
 import { ProviderUpdateRequest } from "../../models/request/provider/provider-update.request";
 import { ProviderVerifyRecoverDeleteRequest } from "../../models/request/provider/provider-verify-recover-delete.request";
@@ -14,4 +16,12 @@ export class ProviderApiServiceAbstraction {
     request: ProviderVerifyRecoverDeleteRequest,
   ) => Promise<any>;
   deleteProvider: (id: string) => Promise<void>;
+  getProviderAddableOrganizations: (providerId: string) => Promise<AddableOrganizationResponse[]>;
+  addOrganizationToProvider: (
+    providerId: string,
+    request: {
+      key: string;
+      organizationId: string;
+    },
+  ) => Promise<void>;
 }
diff --git a/libs/common/src/admin-console/models/response/addable-organization.response.ts b/libs/common/src/admin-console/models/response/addable-organization.response.ts
new file mode 100644
index 00000000000..74ae5f45690
--- /dev/null
+++ b/libs/common/src/admin-console/models/response/addable-organization.response.ts
@@ -0,0 +1,18 @@
+import { BaseResponse } from "@bitwarden/common/models/response/base.response";
+
+export class AddableOrganizationResponse extends BaseResponse {
+  id: string;
+  plan: string;
+  name: string;
+  seats: number;
+  disabled: boolean;
+
+  constructor(response: any) {
+    super(response);
+    this.id = this.getResponseProperty("id");
+    this.plan = this.getResponseProperty("plan");
+    this.name = this.getResponseProperty("name");
+    this.seats = this.getResponseProperty("seats");
+    this.disabled = this.getResponseProperty("disabled");
+  }
+}
diff --git a/libs/common/src/admin-console/services/provider/provider-api.service.ts b/libs/common/src/admin-console/services/provider/provider-api.service.ts
index 2ee921393ff..dc82ec011f4 100644
--- a/libs/common/src/admin-console/services/provider/provider-api.service.ts
+++ b/libs/common/src/admin-console/services/provider/provider-api.service.ts
@@ -1,3 +1,5 @@
+import { AddableOrganizationResponse } from "@bitwarden/common/admin-console/models/response/addable-organization.response";
+
 import { ApiService } from "../../../abstractions/api.service";
 import { ProviderApiServiceAbstraction } from "../../abstractions/provider/provider-api.service.abstraction";
 import { ProviderSetupRequest } from "../../models/request/provider/provider-setup.request";
@@ -44,4 +46,34 @@ export class ProviderApiService implements ProviderApiServiceAbstraction {
   async deleteProvider(id: string): Promise<void> {
     await this.apiService.send("DELETE", "/providers/" + id, null, true, false);
   }
+
+  async getProviderAddableOrganizations(
+    providerId: string,
+  ): Promise<AddableOrganizationResponse[]> {
+    const response = await this.apiService.send(
+      "GET",
+      "/providers/" + providerId + "/clients/addable",
+      null,
+      true,
+      true,
+    );
+
+    return response.map((data: any) => new AddableOrganizationResponse(data));
+  }
+
+  addOrganizationToProvider(
+    providerId: string,
+    request: {
+      key: string;
+      organizationId: string;
+    },
+  ): Promise<void> {
+    return this.apiService.send(
+      "POST",
+      "/providers/" + providerId + "/clients/existing",
+      request,
+      true,
+      false,
+    );
+  }
 }
diff --git a/libs/common/src/enums/feature-flag.enum.ts b/libs/common/src/enums/feature-flag.enum.ts
index 613572bb75b..9b081ce0261 100644
--- a/libs/common/src/enums/feature-flag.enum.ts
+++ b/libs/common/src/enums/feature-flag.enum.ts
@@ -49,6 +49,7 @@ export enum FeatureFlag {
   ResellerManagedOrgAlert = "PM-15814-alert-owners-of-reseller-managed-orgs",
   NewDeviceVerification = "new-device-verification",
   EnableRiskInsightsNotifications = "enable-risk-insights-notifications",
+  PM15179_AddExistingOrgsFromProviderPortal = "PM-15179-add-existing-orgs-from-provider-portal",
 }
 
 export type AllowedFeatureFlagTypes = boolean | number | string;
@@ -108,6 +109,7 @@ export const DefaultFeatureFlagValue = {
   [FeatureFlag.ResellerManagedOrgAlert]: FALSE,
   [FeatureFlag.NewDeviceVerification]: FALSE,
   [FeatureFlag.EnableRiskInsightsNotifications]: FALSE,
+  [FeatureFlag.PM15179_AddExistingOrgsFromProviderPortal]: FALSE,
 } satisfies Record<FeatureFlag, AllowedFeatureFlagTypes>;
 
 export type DefaultFeatureFlagValueType = typeof DefaultFeatureFlagValue;