diff --git a/change/@fluentui-react-field-43eec86b-ad93-4387-bfbe-804eb036cb1a.json b/change/@fluentui-react-field-43eec86b-ad93-4387-bfbe-804eb036cb1a.json
new file mode 100644
index 0000000000000..3d4ed5b0e348d
--- /dev/null
+++ b/change/@fluentui-react-field-43eec86b-ad93-4387-bfbe-804eb036cb1a.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Update MessageBar, Field, and Toast to use Dismiss Diamond icons",
+  "packageName": "@fluentui/react-field",
+  "email": "198982749+Copilot@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@fluentui-react-message-bar-2ba35155-212f-4545-be7f-c76445851fce.json b/change/@fluentui-react-message-bar-2ba35155-212f-4545-be7f-c76445851fce.json
new file mode 100644
index 0000000000000..3886b740aad25
--- /dev/null
+++ b/change/@fluentui-react-message-bar-2ba35155-212f-4545-be7f-c76445851fce.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Update MessageBar, Field, and Toast to use Dismiss Diamond icons",
+  "packageName": "@fluentui/react-message-bar",
+  "email": "198982749+Copilot@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@fluentui-react-toast-95e77c69-5879-4ce7-9e71-f7b708b50f01.json b/change/@fluentui-react-toast-95e77c69-5879-4ce7-9e71-f7b708b50f01.json
new file mode 100644
index 0000000000000..5e7bc6847d499
--- /dev/null
+++ b/change/@fluentui-react-toast-95e77c69-5879-4ce7-9e71-f7b708b50f01.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Update MessageBar, Field, and Toast to use Dismiss Diamond icons",
+  "packageName": "@fluentui/react-toast",
+  "email": "198982749+Copilot@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react-components/react-field/library/src/components/Field/useField.tsx b/packages/react-components/react-field/library/src/components/Field/useField.tsx
index 303d328f75bde..13c4efc8f2c34 100644
--- a/packages/react-components/react-field/library/src/components/Field/useField.tsx
+++ b/packages/react-components/react-field/library/src/components/Field/useField.tsx
@@ -1,12 +1,12 @@
 import * as React from 'react';
 
-import { CheckmarkCircle12Filled, ErrorCircle12Filled, Warning12Filled } from '@fluentui/react-icons';
+import { CheckmarkCircle12Filled, DiamondDismiss12Filled, Warning12Filled } from '@fluentui/react-icons';
 import { Label } from '@fluentui/react-label';
 import { getIntrinsicElementProps, useId, slot } from '@fluentui/react-utilities';
 import type { FieldProps, FieldState } from './Field.types';
 
 const validationMessageIcons = {
-  error: <ErrorCircle12Filled />,
+  error: <DiamondDismiss12Filled />,
   warning: <Warning12Filled />,
   success: <CheckmarkCircle12Filled />,
   none: undefined,
diff --git a/packages/react-components/react-message-bar/library/src/components/MessageBar/getIntentIcon.tsx b/packages/react-components/react-message-bar/library/src/components/MessageBar/getIntentIcon.tsx
index 296cd75bb1ff6..c7e182a7e2fe9 100644
--- a/packages/react-components/react-message-bar/library/src/components/MessageBar/getIntentIcon.tsx
+++ b/packages/react-components/react-message-bar/library/src/components/MessageBar/getIntentIcon.tsx
@@ -1,6 +1,6 @@
 import * as React from 'react';
 import { MessageBarProps } from './MessageBar.types';
-import { CheckmarkCircleFilled, InfoFilled, WarningFilled, DismissCircleFilled } from '@fluentui/react-icons';
+import { CheckmarkCircleFilled, InfoFilled, WarningFilled, DiamondDismissFilled } from '@fluentui/react-icons';
 import type { JSXElement } from '@fluentui/react-utilities';
 
 export function getIntentIcon(intent: MessageBarProps['intent']): JSXElement | null {
@@ -10,7 +10,7 @@ export function getIntentIcon(intent: MessageBarProps['intent']): JSXElement | n
     case 'warning':
       return <WarningFilled />;
     case 'error':
-      return <DismissCircleFilled />;
+      return <DiamondDismissFilled />;
     case 'success':
       return <CheckmarkCircleFilled />;
 
diff --git a/packages/react-components/react-toast/library/src/components/ToastTitle/useToastTitle.tsx b/packages/react-components/react-toast/library/src/components/ToastTitle/useToastTitle.tsx
index 303019f1e73a2..a0416ad8dc53f 100644
--- a/packages/react-components/react-toast/library/src/components/ToastTitle/useToastTitle.tsx
+++ b/packages/react-components/react-toast/library/src/components/ToastTitle/useToastTitle.tsx
@@ -2,7 +2,7 @@
 
 import * as React from 'react';
 
-import { CheckmarkCircleFilled, DismissCircleFilled, InfoFilled, WarningFilled } from '@fluentui/react-icons';
+import { CheckmarkCircleFilled, DiamondDismissFilled, InfoFilled, WarningFilled } from '@fluentui/react-icons';
 import { getIntrinsicElementProps, slot } from '@fluentui/react-utilities';
 import { useBackgroundAppearance } from '@fluentui/react-shared-contexts';
 
@@ -29,7 +29,7 @@ export const useToastTitle_unstable = (props: ToastTitleProps, ref: React.Ref<HT
       defaultIcon = <CheckmarkCircleFilled />;
       break;
     case 'error':
-      defaultIcon = <DismissCircleFilled />;
+      defaultIcon = <DiamondDismissFilled />;
       break;
     case 'warning':
       defaultIcon = <WarningFilled />;