diff --git a/libs/vault/src/cipher-form/components/attachments/cipher-attachments.component.ts b/libs/vault/src/cipher-form/components/attachments/cipher-attachments.component.ts
index 56c3414a12e..a5306606199 100644
--- a/libs/vault/src/cipher-form/components/attachments/cipher-attachments.component.ts
+++ b/libs/vault/src/cipher-form/components/attachments/cipher-attachments.component.ts
@@ -108,11 +108,21 @@ export class CipherAttachmentsComponent implements OnInit, AfterViewInit {
   // eslint-disable-next-line @angular-eslint/prefer-signals
   @Input() submitBtn?: ButtonComponent;
 
+  /** Emits when a file upload is started */
+  // FIXME(https://bitwarden.atlassian.net/browse/CL-903): Migrate to Signals
+  // eslint-disable-next-line @angular-eslint/prefer-output-emitter-ref
+  @Output() onUploadStarted = new EventEmitter<void>();
+
   /** Emits after a file has been successfully uploaded */
   // FIXME(https://bitwarden.atlassian.net/browse/CL-903): Migrate to Signals
   // eslint-disable-next-line @angular-eslint/prefer-output-emitter-ref
   @Output() onUploadSuccess = new EventEmitter<void>();
 
+  /** Emits when a file upload fails */
+  // FIXME(https://bitwarden.atlassian.net/browse/CL-903): Migrate to Signals
+  // eslint-disable-next-line @angular-eslint/prefer-output-emitter-ref
+  @Output() onUploadFailed = new EventEmitter<void>();
+
   /** Emits after a file has been successfully removed */
   // FIXME(https://bitwarden.atlassian.net/browse/CL-903): Migrate to Signals
   // eslint-disable-next-line @angular-eslint/prefer-output-emitter-ref
@@ -196,6 +206,8 @@ export class CipherAttachmentsComponent implements OnInit, AfterViewInit {
 
   /** Save the attachments to the cipher */
   submit = async () => {
+    this.onUploadStarted.emit();
+
     const file = this.attachmentForm.value.file;
     if (file === null) {
       this.toastService.showToast({
@@ -253,6 +265,7 @@ export class CipherAttachmentsComponent implements OnInit, AfterViewInit {
         variant: "error",
         message: errorMessage,
       });
+      this.onUploadFailed.emit();
     }
   };
 
diff --git a/libs/vault/src/cipher-view/attachments/attachments-v2.component.html b/libs/vault/src/cipher-view/attachments/attachments-v2.component.html
index 3b096634069..a8dc22c75ac 100644
--- a/libs/vault/src/cipher-view/attachments/attachments-v2.component.html
+++ b/libs/vault/src/cipher-view/attachments/attachments-v2.component.html
@@ -9,7 +9,9 @@
       [organizationId]="organizationId"
       [admin]="admin"
       [submitBtn]="submitBtn"
+      (onUploadStarted)="uploadStarted()"
       (onUploadSuccess)="uploadSuccessful()"
+      (onUploadFailed)="uploadFailed()"
       (onRemoveSuccess)="removalSuccessful()"
     ></app-cipher-attachments>
   </ng-container>
diff --git a/libs/vault/src/cipher-view/attachments/attachments-v2.component.ts b/libs/vault/src/cipher-view/attachments/attachments-v2.component.ts
index 2796cae08d0..218f5b2c6d3 100644
--- a/libs/vault/src/cipher-view/attachments/attachments-v2.component.ts
+++ b/libs/vault/src/cipher-view/attachments/attachments-v2.component.ts
@@ -1,7 +1,7 @@
 // FIXME: Update this file to be type safe and remove this and next line
 // @ts-strict-ignore
 import { CommonModule } from "@angular/common";
-import { Component, Inject } from "@angular/core";
+import { Component, HostListener, Inject } from "@angular/core";
 
 import { CipherId, OrganizationId } from "@bitwarden/common/types/guid";
 import { UnionOfValues } from "@bitwarden/common/vault/types/union-of-values";
@@ -52,6 +52,7 @@ export class AttachmentsV2Component {
   admin: boolean = false;
   organizationId?: OrganizationId;
   attachmentFormId = CipherAttachmentsComponent.attachmentFormID;
+  private isUploading = false;
 
   /**
    * Constructor for AttachmentsV2Component.
@@ -82,16 +83,54 @@ export class AttachmentsV2Component {
     });
   }
 
+  /**
+   * Prevent browser tab from closing/refreshing during upload.
+   * Shows a confirmation dialog if user tries to leave during an active upload.
+   * This provides additional protection beyond dialogRef.disableClose.
+   * Using arrow function to preserve 'this' context when used as event listener.
+   */
+  @HostListener("window:beforeunload", ["$event"])
+  private handleBeforeUnloadEvent = (event: BeforeUnloadEvent): string | undefined => {
+    if (this.isUploading) {
+      event.preventDefault();
+      // The custom message is not displayed in modern browsers, but MDN docs still recommend setting it for legacy support.
+      const message = "Upload in progress. Are you sure you want to leave?";
+      event.returnValue = message;
+      return message;
+    }
+    return undefined;
+  };
+
+  /**
+   * Called when an attachment upload is started.
+   * Disables closing the dialog to prevent accidental interruption.
+   */
+  uploadStarted() {
+    this.isUploading = true;
+    this.dialogRef.disableClose = true;
+  }
+
   /**
    * Called when an attachment is successfully uploaded.
-   * Closes the dialog with an 'uploaded' result.
+   * Re-enables dialog closing and closes the dialog with an 'uploaded' result.
    */
   uploadSuccessful() {
+    this.isUploading = false;
+    this.dialogRef.disableClose = false;
     this.dialogRef.close({
       action: AttachmentDialogResult.Uploaded,
     });
   }
 
+  /**
+   * Called when an attachment upload fails.
+   * Re-enables closing the dialog.
+   */
+  uploadFailed() {
+    this.isUploading = false;
+    this.dialogRef.disableClose = false;
+  }
+
   /**
    * Called when an attachment is successfully removed.
    * Closes the dialog with a 'removed' result.