diff --git a/backend/src/main/java/online/wesal/wesal/controller/AuthController.java b/backend/src/main/java/online/wesal/wesal/controller/AuthController.java
index 632d7a8..2479b64 100644
--- a/backend/src/main/java/online/wesal/wesal/controller/AuthController.java
+++ b/backend/src/main/java/online/wesal/wesal/controller/AuthController.java
@@ -6,6 +6,7 @@ import jakarta.validation.Valid;
 import online.wesal.wesal.dto.CreateUserRequest;
 import online.wesal.wesal.dto.LoginRequest;
 import online.wesal.wesal.dto.LoginResponse;
+import online.wesal.wesal.dto.UpdateUserRequest;
 import online.wesal.wesal.dto.UsernameSelectionRequest;
 import online.wesal.wesal.entity.User;
 import online.wesal.wesal.service.AuthService;
@@ -67,6 +68,22 @@ public class AuthController {
         }
     }
     
+    @PostMapping("/updateUser")
+    @Operation(summary = "Update user information", description = "Update authenticated user's fcmToken, displayName, avatar, or password")
+    public ResponseEntity<Map<String, Object>> updateUser(@Valid @RequestBody UpdateUserRequest request) {
+        try {
+            User user = userService.updateUser(
+                request.getFcmToken(),
+                request.getDisplayName(),
+                request.getAvatar(),
+                request.getPassword()
+            );
+            return ResponseEntity.ok(Map.of("status", 200, "user", user));
+        } catch (RuntimeException e) {
+            return ResponseEntity.badRequest().body(Map.of("status", 400, "message", e.getMessage()));
+        }
+    }
+    
     @PostMapping("/admin/createUser")
     @Operation(summary = "Create new user (Admin only)", description = "Creates a new user - requires admin privileges")
     public ResponseEntity<?> createUser(@Valid @RequestBody CreateUserRequest request) {
diff --git a/backend/src/main/java/online/wesal/wesal/dto/UpdateUserRequest.java b/backend/src/main/java/online/wesal/wesal/dto/UpdateUserRequest.java
new file mode 100644
index 0000000..1f5b171
--- /dev/null
+++ b/backend/src/main/java/online/wesal/wesal/dto/UpdateUserRequest.java
@@ -0,0 +1,49 @@
+package online.wesal.wesal.dto;
+
+import jakarta.validation.constraints.Size;
+
+public class UpdateUserRequest {
+    
+    private String fcmToken;
+    
+    private String displayName;
+    
+    private String avatar;
+    
+    @Size(min = 8, message = "Password must be at least 8 characters long")
+    private String password;
+    
+    public UpdateUserRequest() {}
+    
+    public String getFcmToken() {
+        return fcmToken;
+    }
+    
+    public void setFcmToken(String fcmToken) {
+        this.fcmToken = fcmToken;
+    }
+    
+    public String getDisplayName() {
+        return displayName;
+    }
+    
+    public void setDisplayName(String displayName) {
+        this.displayName = displayName;
+    }
+    
+    public String getAvatar() {
+        return avatar;
+    }
+    
+    public void setAvatar(String avatar) {
+        this.avatar = avatar;
+    }
+    
+    public String getPassword() {
+        return password;
+    }
+    
+    public void setPassword(String password) {
+        this.password = password;
+    }
+}
\ No newline at end of file
diff --git a/backend/src/main/java/online/wesal/wesal/service/UserService.java b/backend/src/main/java/online/wesal/wesal/service/UserService.java
index 9a0e790..9dd0f91 100644
--- a/backend/src/main/java/online/wesal/wesal/service/UserService.java
+++ b/backend/src/main/java/online/wesal/wesal/service/UserService.java
@@ -55,4 +55,26 @@ public class UserService {
         User user = new User(email, passwordEncoder.encode(password), displayName);
         return userRepository.save(user);
     }
+    
+    public User updateUser(String fcmToken, String displayName, String avatar, String password) {
+        User user = getCurrentUser();
+        
+        if (fcmToken != null && !fcmToken.trim().isEmpty()) {
+            user.setFcmToken(fcmToken);
+        }
+        
+        if (displayName != null && !displayName.trim().isEmpty()) {
+            user.setDisplayName(displayName);
+        }
+        
+        if (avatar != null) {
+            user.setAvatar(avatar);
+        }
+        
+        if (password != null && !password.trim().isEmpty()) {
+            user.setPassword(passwordEncoder.encode(password));
+        }
+        
+        return userRepository.save(user);
+    }
 }
\ No newline at end of file