diff --git a/FirebaseAuthUI/FUIAuth.h b/FirebaseAuthUI/FUIAuth.h
index 8fa95b3ff2a..80e6f01f298 100644
--- a/FirebaseAuthUI/FUIAuth.h
+++ b/FirebaseAuthUI/FUIAuth.h
@@ -190,6 +190,12 @@ __attribute__((deprecated("Instead use authUI:didSignInWithAuthDataResult:error:
  */
 @property(nonatomic, copy, nullable) NSURL *TOSURL;
 
+/** @property shouldAutoUpgradeAnonymousUsers
+    @brief Whether to enable auto upgrading of anonymous accounts, defaults to NO.
+ */
+@property(nonatomic, assign, getter=shouldAutoUpgradeAnonymousUsers) BOOL
+    shouldAutoUpgradeAnonymousUsers;
+
 /** @property delegate
     @brief A delegate that receives callbacks or provides custom UI for @c FUIAuth.
  */
diff --git a/FirebaseAuthUI/FUIAuth.m b/FirebaseAuthUI/FUIAuth.m
index af789c66ec5..63245d1e77a 100644
--- a/FirebaseAuthUI/FUIAuth.m
+++ b/FirebaseAuthUI/FUIAuth.m
@@ -174,37 +174,78 @@ - (void)signInWithProviderUI:(id<FUIAuthProvider>)providerUI
       return;
     }
 
-    [self.auth signInAndRetrieveDataWithCredential:credential
-                                        completion:^(FIRAuthDataResult *_Nullable authResult,
-                                                     NSError *_Nullable error) {
-      if (error && error.code == FIRAuthErrorCodeAccountExistsWithDifferentCredential) {
-        NSString *email = error.userInfo[kErrorUserInfoEmailKey];
-        [self handleAccountLinkingForEmail:email
-                             newCredential:credential
-                  presentingViewController:presentingViewController
-                              singInResult:result];
-        return;
+    // Block to complete sign-in
+    void (^completeSignInBlock)(FIRAuthDataResult *, NSError *) = ^(FIRAuthDataResult *authResult,
+                                                                    NSError *error) {
+      if (result) {
+        result(authResult.user, nil);
       }
-
-      if (error) {
-        if (result) {
-          result(nil, error);
-        }
-        [self invokeResultCallbackWithAuthDataResult:nil error:error];
+      // Hide Auth Picker Controller which was presented modally.
+      if (isAuthPickerShown && presentingViewController.presentingViewController) {
+        [presentingViewController dismissViewControllerAnimated:YES completion:^{
+          [self invokeResultCallbackWithAuthDataResult:authResult error:error];
+        }];
       } else {
-        if (result) {
-          result(authResult.user, nil);
+        [self invokeResultCallbackWithAuthDataResult:authResult error:error];
+      }
+    };
+
+    // Check for the presence of an anonymous user and whether automatic upgrade is enabled.
+    if (_auth.currentUser.isAnonymous && [FUIAuth defaultAuthUI].shouldAutoUpgradeAnonymousUsers) {
+      [_auth.currentUser
+          linkAndRetrieveDataWithCredential:credential
+                                 completion:^(FIRAuthDataResult *_Nullable authResult,
+                                              NSError * _Nullable error) {
+        if (error) {
+          // Check for "credential in use" conflict error and handle appropriately.
+          if (error.code == FIRAuthErrorCodeCredentialAlreadyInUse) {
+            NSError *mergeError;
+            FIRAuthCredential *newCredential = credential;
+            // Check for and handle special case for Phone Auth Provider.
+            if (providerUI.providerID == FIRPhoneAuthProviderID) {
+              // Obtain temporary Phone Auth provider.
+              newCredential = error.userInfo[FIRAuthUpdatedCredentialKey];
+            }
+            NSDictionary *userInfo = @{
+              FUIAuthCredentialKey : newCredential,
+            };
+            mergeError = [NSError errorWithDomain:FUIAuthErrorDomain
+                                             code:FUIAuthErrorCodeMergeConflict
+                                         userInfo:userInfo];
+            result(nil, mergeError);
+            completeSignInBlock(authResult, mergeError);
+          } else {
+            if (!isAuthPickerShown || error.code != FUIAuthErrorCodeUserCancelledSignIn) {
+              [self invokeResultCallbackWithAuthDataResult:nil error:error];
+            }
+            if (result) {
+              result(nil, error);
+            }
+          }
         }
-        // Hide Auth Picker Controller which was presented modally.
-        if (isAuthPickerShown && presentingViewController.presentingViewController) {
-          [presentingViewController dismissViewControllerAnimated:YES completion:^{
-            [self invokeResultCallbackWithAuthDataResult:authResult error:nil];
-          }];
-        } else {
-          [self invokeResultCallbackWithAuthDataResult:authResult error:nil];
+      }];
+    } else {
+      [self.auth signInAndRetrieveDataWithCredential:credential
+                                          completion:^(FIRAuthDataResult *_Nullable authResult,
+                                                       NSError *_Nullable error) {
+        if (error && error.code == FIRAuthErrorCodeAccountExistsWithDifferentCredential) {
+          NSString *email = error.userInfo[kErrorUserInfoEmailKey];
+          [self handleAccountLinkingForEmail:email
+                               newCredential:credential
+                    presentingViewController:presentingViewController
+                                singInResult:result];
+          return;
         }
-      }
-    }];
+        if (error) {
+          if (result) {
+            result(nil, error);
+          }
+          [self invokeResultCallbackWithAuthDataResult:nil error:error];
+          return;
+        }
+        completeSignInBlock(authResult, nil);
+      }];
+    }
   }];
 }
 
diff --git a/FirebaseAuthUI/FUIAuthErrors.h b/FirebaseAuthUI/FUIAuthErrors.h
index bee0bb225a5..87cfccf6e0d 100644
--- a/FirebaseAuthUI/FUIAuthErrors.h
+++ b/FirebaseAuthUI/FUIAuthErrors.h
@@ -28,6 +28,12 @@ extern NSString *const FUIAuthErrorDomain;
  */
 extern NSString *const FUIAuthErrorUserInfoProviderIDKey;
 
+/** @bar FUIAuthCredentialKey
+    @brief The key used to obtain the credential stored within the userInfo dictionary of the
+        error, if availalble.
+ */
+extern NSString *const FUIAuthCredentialKey;
+
 /** @var FUIAuthErrorCode
     @brief Error codes used by FUIAuth.
  */
@@ -50,6 +56,13 @@ typedef NS_ENUM(NSUInteger, FUIAuthErrorCode) {
           key @c FUIAuthErrorUserInfoProviderIDKey).
    */
   FUIAuthErrorCodeCantFindProvider = 3,
+
+  /** @var FUIAuthErrorCodeMergeConflict
+      @brief Indicates that a merge conflict occurred while trying to automatically upgrade an
+          anonymous user. The non-anonymous credential can be obtained from the userInfo dictionary
+          of the corresponding NSError using the @c FUIAuthCredentialKey.
+   */
+  FUIAuthErrorCodeMergeConflict = 4,
 };
 
 NS_ASSUME_NONNULL_END
diff --git a/FirebaseAuthUI/FUIAuthErrors.m b/FirebaseAuthUI/FUIAuthErrors.m
index 90cc468826a..dc7df99a40d 100644
--- a/FirebaseAuthUI/FUIAuthErrors.m
+++ b/FirebaseAuthUI/FUIAuthErrors.m
@@ -19,3 +19,5 @@
 NSString *const FUIAuthErrorDomain = @"FUIAuthErrorDomain";
 
 NSString *const FUIAuthErrorUserInfoProviderIDKey = @"FUIAuthErrorUserInfoProviderIDKey";
+
+NSString *const FUIAuthCredentialKey = @"FUIAuthCredentialKey";
diff --git a/FirebasePhoneAuthUI/FUIPhoneVerificationViewController.m b/FirebasePhoneAuthUI/FUIPhoneVerificationViewController.m
index 2da2deb485d..8d370e6cee5 100644
--- a/FirebasePhoneAuthUI/FUIPhoneVerificationViewController.m
+++ b/FirebasePhoneAuthUI/FUIPhoneVerificationViewController.m
@@ -187,7 +187,9 @@ - (void)onNext:(NSString *)verificationCode {
                             result:^(FIRUser *_Nullable user, NSError *_Nullable error) {
     [self decrementActivity];
     self.navigationItem.rightBarButtonItem.enabled = YES;
-    if (!error || error.code == FUIAuthErrorCodeUserCancelledSignIn) {
+    if (!error ||
+        error.code == FUIAuthErrorCodeUserCancelledSignIn ||
+        error.code == FUIAuthErrorCodeMergeConflict) {
       [self.navigationController dismissViewControllerAnimated:YES completion:nil];
     } else {
       UIAlertController *alertController = [FUIPhoneAuth alertControllerForError:error
diff --git a/samples/objc/FirebaseUI-demo-objc/Samples/Auth/FUIAuthViewController.m b/samples/objc/FirebaseUI-demo-objc/Samples/Auth/FUIAuthViewController.m
index db90e18dc8f..13a05264ee6 100644
--- a/samples/objc/FirebaseUI-demo-objc/Samples/Auth/FUIAuthViewController.m
+++ b/samples/objc/FirebaseUI-demo-objc/Samples/Auth/FUIAuthViewController.m
@@ -148,8 +148,18 @@ - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPa
 
 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
   if (indexPath.section == kSectionsAnonymousSignIn && indexPath.row == 0) {
-    if (_authUI.auth.currentUser.isAnonymous) {
-      [self showAlertWithTitlte:@"" message:@"Already signed in anonymously"];
+    FIRUser *currentUser = self.authUI.auth.currentUser;
+    if (currentUser.isAnonymous) {
+      // If the user is anonymous, delete the user to avoid dangling anonymous users.
+      if (currentUser.isAnonymous) {
+        [currentUser deleteWithCompletion:^(NSError * _Nullable error) {
+          if (error) {
+            [self showAlertWithTitlte:@"Error" message:error.localizedDescription];
+            return;
+          }
+          [self showAlertWithTitlte:@"" message:@"Anonymous user deleted"];
+        }];
+      }
       [tableView deselectRowAtIndexPath:indexPath animated:NO];
       return;
     }
@@ -179,12 +189,15 @@ - (void)updateUI:(FIRAuth * _Nonnull) auth withUser:(FIRUser *_Nullable) user {
     self.cellUID.textLabel.text = user.uid;
 
     // If the user is anonymous, delete the user to avoid dangling anonymous users.
-    if (self.authUI.auth.currentUser.isAnonymous) {
-      self.buttonAuthorization.title = @"Delete Anonymous User";
-    } else {
+    if (auth.currentUser.isAnonymous) {
+      [_anonymousSignIn.textLabel setText:@"Delete Anonymous User"];
+    }
+    else {
+      [_anonymousSignIn.textLabel setText:@"Sign In Anonymously"];
       self.buttonAuthorization.title = @"Sign Out";
     }
   } else {
+    [_anonymousSignIn.textLabel setText:@"Sign In Anonymously"];
     self.cellSignIn.textLabel.text = @"Not signed-in";
     self.cellName.textLabel.text = @"";
     self.cellEmail.textLabel.text = @"";
@@ -215,8 +228,8 @@ - (IBAction)onAuthUIDelegateChanged:(UISwitch *)sender {
 }
 
 - (IBAction)onAuthorization:(id)sender {
-  if (!self.auth.currentUser) {
-
+  if (!_auth.currentUser || _auth.currentUser.isAnonymous) {
+    FUIAuth.defaultAuthUI.shouldAutoUpgradeAnonymousUsers = YES;
     _authUI.providers = [self getListOfIDPs];
     _authUI.signInWithEmailHidden = ![self isEmailEnabled];
 
@@ -247,13 +260,31 @@ - (void)authUI:(FUIAuth *)authUI
   if (error) {
     if (error.code == FUIAuthErrorCodeUserCancelledSignIn) {
       [self showAlertWithTitlte:@"Error" message:error.localizedDescription];
-    } else {
-      NSError *detailedError = error.userInfo[NSUnderlyingErrorKey];
-      if (!detailedError) {
-        detailedError = error;
-      }
-      NSLog(@"ERROR: %@", detailedError.localizedDescription);
+      return;
+    }
+    if (error.code == FUIAuthErrorCodeMergeConflict) {
+      FIRAuthCredential *credential = error.userInfo[FUIAuthCredentialKey];
+      NSString *anonymousUserID = authUI.auth.currentUser.uid;
+      NSString *messsage = [NSString stringWithFormat:@"A merge conflict occurred. The old user ID "
+          "was: %@. You are now signed in with the following credential type: %@", anonymousUserID,
+          [credential.provider uppercaseString]];
+      [self showAlertWithTitlte:@"Merge Conflict" message:messsage];
+      NSLog(@"%@", messsage);
+      [[FUIAuth defaultAuthUI].auth
+          signInAndRetrieveDataWithCredential:credential
+                                   completion:^(FIRAuthDataResult *_Nullable authResult,
+                                                NSError *_Nullable error) {
+        if (error) {
+          NSLog(@"%@",error.description);
+        }
+      }];
+      return;
+    }
+    NSError *detailedError = error.userInfo[NSUnderlyingErrorKey];
+    if (!detailedError) {
+      detailedError = error;
     }
+    NSLog(@"ERROR: %@", detailedError.localizedDescription);
   }
 }
 
@@ -279,21 +310,9 @@ - (NSString *)getAllIdTokens {
 
 - (void)signOut {
   NSError *error;
-  FIRUser *currentUser = self.authUI.auth.currentUser;
-  // If the user is anonymous, delete the user to avoid dangling anonymous users.
-  if (currentUser.isAnonymous) {
-    [currentUser deleteWithCompletion:^(NSError * _Nullable error) {
-      if (error) {
-        [self showAlertWithTitlte:@"Error" message:error.localizedDescription];
-        return;
-      }
-      [self showAlertWithTitlte:@"" message:@"Anonymous user deleted"];
-    }];
-  } else {
-    [self.authUI signOutWithError:&error];
-    if (error) {
-      [self showAlertWithTitlte:@"Error" message:error.localizedDescription];
-    }
+  [self.authUI signOutWithError:&error];
+  if (error) {
+    [self showAlertWithTitlte:@"Error" message:error.localizedDescription];
   }
 }