diff --git a/src/client/Microsoft.Identity.Client/AuthenticationResult.cs b/src/client/Microsoft.Identity.Client/AuthenticationResult.cs
index 34358b65bd..779de9abd9 100644
--- a/src/client/Microsoft.Identity.Client/AuthenticationResult.cs
+++ b/src/client/Microsoft.Identity.Client/AuthenticationResult.cs
@@ -218,7 +218,9 @@ private AuthenticationResult(
             }
 
             UniqueId = msalIdTokenCacheItem?.IdToken?.GetUniqueId();
-            TenantId = msalIdTokenCacheItem?.IdToken?.TenantId;
+            // For client credentials flow, ID token is not available, so fall back to access token's tenant
+            // See https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/5743
+            TenantId = msalIdTokenCacheItem?.IdToken?.TenantId ?? msalAccessTokenCacheItem?.TenantId;
             IdToken = msalIdTokenCacheItem?.Secret;
             SpaAuthCode = spaAuthCode;
             _authenticationScheme = authenticationScheme;
diff --git a/tests/Microsoft.Identity.Test.Integration.netcore/HeadlessTests/ClientCredentialsTests.NetFwk.cs b/tests/Microsoft.Identity.Test.Integration.netcore/HeadlessTests/ClientCredentialsTests.NetFwk.cs
index a7ad4a511f..56d42c363f 100644
--- a/tests/Microsoft.Identity.Test.Integration.netcore/HeadlessTests/ClientCredentialsTests.NetFwk.cs
+++ b/tests/Microsoft.Identity.Test.Integration.netcore/HeadlessTests/ClientCredentialsTests.NetFwk.cs
@@ -221,6 +221,130 @@ public async Task WithOnBeforeTokenRequest_TestAsync(Cloud cloud, TargetFramewor
             Assert.AreEqual(TokenSource.Cache, authResult.AuthenticationResultMetadata.TokenSource);
         }
 
+        [TestMethod]
+        [DataRow(TargetFrameworks.NetCore)]
+        [Description("Issue #5743: Validates that AuthenticationResult.TenantId is not null for client credentials")]
+        public async Task ClientCredentials_TenantId_ShouldNotBeNull_Issue5743_Async(TargetFrameworks runOn)
+        {
+            runOn.AssertFramework();
+
+            var appConfig = await LabResponseHelper.GetAppConfigAsync(KeyVaultSecrets.AppS2S).ConfigureAwait(false);
+            var cert = CertificateHelper.FindCertificateByName(TestConstants.AutomationTestCertName);
+            string[] scopes = new[] { "https://vault.azure.net/.default" };
+
+            var confidentialApp = ConfidentialClientApplicationBuilder
+                .Create(appConfig.AppId)
+                .WithAuthority(appConfig.Authority, true)
+                .WithCertificate(cert)
+                .WithTestLogging()
+                .Build();
+
+            // First call - from identity provider
+            var result = await confidentialApp
+                .AcquireTokenForClient(scopes)
+                .ExecuteAsync()
+                .ConfigureAwait(false);
+
+            Assert.IsNotNull(result.TenantId,
+                "TenantId should not be null in AuthenticationResult for client credentials flow!");
+            Assert.AreEqual(appConfig.TenantId, result.TenantId,
+                "TenantId should match the configured tenant");
+            Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
+
+            // Second call - from cache
+            result = await confidentialApp
+                .AcquireTokenForClient(scopes)
+                .ExecuteAsync()
+                .ConfigureAwait(false);
+
+            Assert.IsNotNull(result.TenantId,
+                "TenantId should not be null even when token comes from cache!");
+            Assert.AreEqual(appConfig.TenantId, result.TenantId,
+                "Cached token should preserve TenantId");
+            Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);
+        }
+
+        [TestMethod]
+        [DataRow(TargetFrameworks.NetCore)]
+        [Description("Issue #5743: Validates TenantId when using WithTenantId override with organizations authority")]
+        public async Task ClientCredentials_WithTenantIdOverride_ShouldPopulateTenantId_Issue5743_Async(TargetFrameworks runOn)
+        {
+            runOn.AssertFramework();
+
+            var appConfig = await LabResponseHelper.GetAppConfigAsync(KeyVaultSecrets.AppS2S).ConfigureAwait(false);
+            var cert = CertificateHelper.FindCertificateByName(TestConstants.AutomationTestCertName);
+            string[] scopes = new[] { "https://vault.azure.net/.default" };
+
+            // Build app with "organizations" authority
+            var confidentialApp = ConfidentialClientApplicationBuilder
+                .Create(appConfig.AppId)
+                .WithAuthority("https://login.microsoftonline.com/organizations", true)
+                .WithCertificate(cert)
+                .WithTestLogging()
+                .Build();
+
+            // Request token with specific tenant override
+            var result = await confidentialApp
+                .AcquireTokenForClient(scopes)
+                .WithTenantId(appConfig.TenantId)
+                .ExecuteAsync()
+                .ConfigureAwait(false);
+
+            // ❌ BUG #5743: This assertion will FAIL
+            Assert.IsNotNull(result.TenantId,
+                "❌ BUG #5743: TenantId must be populated when using WithTenantId override!");
+            Assert.AreEqual(appConfig.TenantId, result.TenantId,
+                "TenantId should match the overridden tenant, not 'organizations'");
+            Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
+
+            // Second call from cache
+            result = await confidentialApp
+                .AcquireTokenForClient(scopes)
+                .WithTenantId(appConfig.TenantId)
+                .ExecuteAsync()
+                .ConfigureAwait(false);
+
+            Assert.IsNotNull(result.TenantId,
+                "❌ BUG #5743: Cached token should also have TenantId populated!");
+            Assert.AreEqual(appConfig.TenantId, result.TenantId);
+            Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);
+        }
+
+        [TestMethod]
+        [DataRow(TargetFrameworks.NetCore)]
+        [Description("Issue #5743: Rapid tenant switching should maintain correct TenantId")]
+        public async Task ClientCredentials_RapidTenantSwitching_Issue5743_Async(TargetFrameworks runOn)
+        {
+            runOn.AssertFramework();
+
+            var appConfig = await LabResponseHelper.GetAppConfigAsync(KeyVaultSecrets.AppS2S).ConfigureAwait(false);
+            var cert = CertificateHelper.FindCertificateByName(TestConstants.AutomationTestCertName);
+            string[] scopes = new[] { "https://vault.azure.net/.default" };
+
+            var confidentialApp = ConfidentialClientApplicationBuilder
+                .Create(appConfig.AppId)
+                .WithAuthority("https://login.microsoftonline.com/organizations", true)
+                .WithCertificate(cert)
+                .WithTestLogging()
+                .Build();
+
+            // Rapidly switch between same tenant multiple times with force refresh
+            for (int i = 0; i < 10; i++)
+            {   
+                var result = await confidentialApp
+                    .AcquireTokenForClient(scopes)
+                    .WithTenantId(appConfig.TenantId)
+                    .WithForceRefresh(true)
+                    .ExecuteAsync()
+                    .ConfigureAwait(false);
+
+                Assert.IsNotNull(result.TenantId,
+                    $"❌ BUG #5743: Iteration {i}: TenantId should not be null!");
+                Assert.AreEqual(appConfig.TenantId, result.TenantId,
+                    $"Iteration {i}: TenantId should match requested tenant");
+            }
+        }
+
         [RunOn(TargetFrameworks.NetCore)]
         public async Task ByRefreshTokenTestAsync()
         {
@@ -357,6 +481,12 @@ private async Task RunClientCredsAsync(Cloud cloud, CredentialType credentialTyp
             MsalAssert.AssertAuthResult(authResult);
             appCacheRecorder.AssertAccessCounts(1, 1);
             Assert.AreEqual(TokenSource.IdentityProvider, authResult.AuthenticationResultMetadata.TokenSource);
+
+            // Issue #5743: Validate TenantId is populated
+            Assert.IsNotNull(authResult.TenantId, 
+                "❌ BUG #5743: TenantId should not be null for client credentials!");
+            Assert.AreEqual(tenantId, authResult.TenantId,
+                "TenantId should match the tenant from authority");
             Assert.IsTrue(appCacheRecorder.LastAfterAccessNotificationArgs.IsApplicationCache);
             Assert.IsTrue(appCacheRecorder.LastAfterAccessNotificationArgs.HasTokens);
             Assert.AreEqual(correlationId, appCacheRecorder.LastAfterAccessNotificationArgs.CorrelationId);
@@ -385,6 +515,12 @@ private async Task RunClientCredsAsync(Cloud cloud, CredentialType credentialTyp
 
             appCacheRecorder.AssertAccessCounts(2, 1);
             Assert.AreEqual(TokenSource.Cache, authResult.AuthenticationResultMetadata.TokenSource);
+
+            // Issue #5743: Validate TenantId is preserved in cached result
+            Assert.IsNotNull(authResult.TenantId,
+                "❌ BUG #5743: TenantId should not be null even from cache!");
+            Assert.AreEqual(tenantId, authResult.TenantId,
+                "Cached token should preserve TenantId");
             Assert.IsTrue(appCacheRecorder.LastAfterAccessNotificationArgs.IsApplicationCache);
             Assert.IsTrue(appCacheRecorder.LastAfterAccessNotificationArgs.HasTokens);
             Assert.AreNotEqual(correlationId, appCacheRecorder.LastAfterAccessNotificationArgs.CorrelationId);