diff --git a/src/libs/PersonalDetailsUtils.ts b/src/libs/PersonalDetailsUtils.ts
index 7568be651762..06d00b844836 100644
--- a/src/libs/PersonalDetailsUtils.ts
+++ b/src/libs/PersonalDetailsUtils.ts
@@ -328,9 +328,9 @@ function getFormattedAddress(privatePersonalDetails: OnyxEntry<PrivatePersonalDe
  * @param personalDetail - details object
  * @returns - The effective display name
  */
-function getEffectiveDisplayName(personalDetail?: PersonalDetails): string | undefined {
+function getEffectiveDisplayName(formatPhoneNumber: LocaleContextProps['formatPhoneNumber'], personalDetail?: PersonalDetails): string | undefined {
     if (personalDetail) {
-        return formatPhoneNumberUtils(personalDetail?.login ?? '') || personalDetail.displayName;
+        return formatPhoneNumber(personalDetail?.login ?? '') || personalDetail.displayName;
     }
 
     return undefined;
diff --git a/src/libs/ReportActionsUtils.ts b/src/libs/ReportActionsUtils.ts
index d4a3fe1a8f86..0120cb0d7ad8 100644
--- a/src/libs/ReportActionsUtils.ts
+++ b/src/libs/ReportActionsUtils.ts
@@ -1424,7 +1424,7 @@ function getMemberChangeMessageElements(reportAction: OnyxEntry<ReportAction>, g
 
     const mentionElements = targetAccountIDs.map((accountID): MemberChangeMessageUserMentionElement => {
         const personalDetail = personalDetails.find((personal) => personal.accountID === accountID);
-        const handleText = getEffectiveDisplayName(personalDetail) ?? translateLocal('common.hidden');
+        const handleText = getEffectiveDisplayName(formatPhoneNumber, personalDetail) ?? translateLocal('common.hidden');
 
         return {
             kind: 'userMention',
@@ -1888,7 +1888,7 @@ function getActionableMentionWhisperMessage(reportAction: OnyxEntry<ReportAction
     const personalDetails = getPersonalDetailsByIDs({accountIDs: targetAccountIDs, currentUserAccountID: 0});
     const mentionElements = targetAccountIDs.map((accountID): string => {
         const personalDetail = personalDetails.find((personal) => personal.accountID === accountID);
-        const displayName = getEffectiveDisplayName(personalDetail);
+        const displayName = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
         const handleText = isEmpty(displayName) ? translateLocal('common.hidden') : displayName;
         return `<mention-user accountID=${accountID}>@${handleText}</mention-user>`;
     });
diff --git a/src/libs/ReportUtils.ts b/src/libs/ReportUtils.ts
index d5a6faada348..536ee85087c7 100644
--- a/src/libs/ReportUtils.ts
+++ b/src/libs/ReportUtils.ts
@@ -4818,7 +4818,7 @@ function getAdminRoomInvitedParticipants(parentReportAction: OnyxEntry<ReportAct
     const personalDetails = getPersonalDetailsByIDs({accountIDs: originalMessage?.targetAccountIDs ?? [], currentUserAccountID: 0});
 
     const participants = personalDetails.map((personalDetail) => {
-        const name = getEffectiveDisplayName(personalDetail);
+        const name = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
         if (name && name?.length > 0) {
             return name;
         }
diff --git a/tests/unit/libs/PersonalDetailsUtilsTest.ts b/tests/unit/libs/PersonalDetailsUtilsTest.ts
index 49115a87cff2..5511066460b3 100644
--- a/tests/unit/libs/PersonalDetailsUtilsTest.ts
+++ b/tests/unit/libs/PersonalDetailsUtilsTest.ts
@@ -1,9 +1,98 @@
 import Onyx from 'react-native-onyx';
-import {getPersonalDetailsOnyxDataForOptimisticUsers} from '@libs/PersonalDetailsUtils';
+import {getEffectiveDisplayName, getPersonalDetailsOnyxDataForOptimisticUsers} from '@libs/PersonalDetailsUtils';
 import ONYXKEYS from '@src/ONYXKEYS';
+import type {PersonalDetails} from '@src/types/onyx';
 import {formatPhoneNumber} from '../../utils/TestHelper';
 
 describe('PersonalDetailsUtils', () => {
+    describe('getEffectiveDisplayName', () => {
+        test('should return undefined when personalDetail is undefined', () => {
+            const result = getEffectiveDisplayName(formatPhoneNumber, undefined);
+            expect(result).toBeUndefined();
+        });
+
+        test('should return undefined when personalDetail has neither login nor displayName', () => {
+            const personalDetail: PersonalDetails = {accountID: 123};
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBeUndefined();
+        });
+
+        test('should return displayName when login is empty or null but displayName exists', () => {
+            const personalDetail1: PersonalDetails = {accountID: 123, displayName: 'John Doe', login: ''};
+            const personalDetail2: PersonalDetails = {accountID: 456, displayName: 'Jane Smith', login: null as unknown as string}; // Simulate null login
+
+            let result = getEffectiveDisplayName(formatPhoneNumber, personalDetail1);
+            expect(result).toBe('John Doe');
+
+            result = getEffectiveDisplayName(formatPhoneNumber, personalDetail2);
+            expect(result).toBe('Jane Smith');
+        });
+
+        test('should return login (email) when only login exists (not a phone number)', () => {
+            const personalDetail: PersonalDetails = {accountID: 123, login: 'john.doe@example.com'};
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('john.doe@example.com');
+        });
+
+        test('should return national format for phone login if from the same region (US)', () => {
+            const personalDetail: PersonalDetails = {accountID: 123, login: '+15551234567'};
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('+1 555-123-4567');
+        });
+
+        test('should return international format for phone login if from a different region (GB)', () => {
+            const personalDetail: PersonalDetails = {accountID: 123, login: '+442079460000'};
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('+44 20 7946 0000');
+        });
+
+        test('should return formatted login (email) when both login and displayName exist (login takes precedence)', () => {
+            const personalDetail: PersonalDetails = {
+                accountID: 123,
+                login: 'john.doe@example.com',
+                displayName: 'John Doe Full Name',
+            };
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('john.doe@example.com');
+        });
+
+        test('should return formatted login (phone) when both login (same region) and displayName exist', () => {
+            const personalDetail: PersonalDetails = {
+                accountID: 123,
+                login: '+15551234567',
+                displayName: 'John Doe Full Name',
+            };
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('+1 555-123-4567');
+        });
+
+        test('should return formatted login (phone) when both login (different region) and displayName exist', () => {
+            const personalDetail: PersonalDetails = {
+                accountID: 123,
+                login: '+442079460000',
+                displayName: 'Jane Smith Full Name',
+            };
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('+44 20 7946 0000');
+        });
+
+        test('should correctly handle login with SMS domain', () => {
+            const personalDetail: PersonalDetails = {
+                accountID: 123,
+                login: `+18005550000`,
+                displayName: 'SMS User',
+            };
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('(800) 555-0000');
+        });
+
+        test('should fall back to displayName if formatted login is an empty string and displayName exists', () => {
+            const personalDetail: PersonalDetails = {accountID: 123, login: '', displayName: 'Fallback Name'};
+            const result = getEffectiveDisplayName(formatPhoneNumber, personalDetail);
+            expect(result).toBe('Fallback Name');
+        });
+    });
+
     describe('getPersonalDetailsOnyxDataForOptimisticUsers', () => {
         test('should return correct optimistic and finally data', () => {
             const newLogins = ['3322076524', 'test2@test.com', '+14185438090'];