diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Controllers/BookmarkController.java b/backend/src/main/java/com/group1/programminglanguagesforum/Controllers/BookmarkController.java
index 8731efee..f2d2b39a 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Controllers/BookmarkController.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Controllers/BookmarkController.java
@@ -3,12 +3,13 @@
 import com.group1.programminglanguagesforum.Constants.EndpointConstants;
 import com.group1.programminglanguagesforum.DTOs.Responses.BookmarkQuestionResponseDto;
 import com.group1.programminglanguagesforum.DTOs.Responses.QuestionSummaryDto;
-import com.group1.programminglanguagesforum.DTOs.Responses.ErrorResponse;
 import com.group1.programminglanguagesforum.DTOs.Responses.GenericApiResponse;
 import com.group1.programminglanguagesforum.Exceptions.UnauthorizedAccessException;
 import com.group1.programminglanguagesforum.Exceptions.ExceptionResponseHandler;
 import com.group1.programminglanguagesforum.Services.BookmarkService;
 import com.group1.programminglanguagesforum.Util.ApiResponseBuilder;
+
+import jakarta.persistence.EntityExistsException;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -19,7 +20,6 @@
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
-import java.util.Arrays;
 import java.util.List;
 import java.util.NoSuchElementException;
 
@@ -40,22 +40,12 @@ public ResponseEntity<GenericApiResponse<BookmarkQuestionResponseDto>> bookmarkQ
                     bookmarkQuestionResponseDto
             );
             return buildResponse(genericApiResponse, HttpStatus.OK);
-
-
         } catch (NoSuchElementException e) {
-            ErrorResponse errorResponse = ErrorResponse.builder()
-                    .errorMessage(e.getMessage())
-                    .stackTrace(Arrays.toString(e.getStackTrace()))
-                    .build();
-            GenericApiResponse<BookmarkQuestionResponseDto> genericApiResponse = ApiResponseBuilder.buildErrorResponse(
-                    BookmarkQuestionResponseDto.class,
-                    "An error occurred while bookmarking the question",
-                    HttpStatus.NOT_FOUND.value(),
-                    errorResponse
-            );
-            return buildResponse(genericApiResponse, HttpStatus.NOT_FOUND);
+            return ExceptionResponseHandler.NoSuchElementException(e);
         } catch (UnauthorizedAccessException e) {
             return ExceptionResponseHandler.UnauthorizedAccessException(e);
+        } catch (EntityExistsException e) {
+            return ExceptionResponseHandler.EntityExistsException(e);
         }
     }
 
@@ -70,19 +60,8 @@ public ResponseEntity<GenericApiResponse<BookmarkQuestionResponseDto>> removeBoo
                     bookmarkQuestionResponseDto
             );
             return buildResponse(genericApiResponse, HttpStatus.OK);
-        }
-        catch (NoSuchElementException e) {
-            ErrorResponse errorResponse = ErrorResponse.builder()
-                    .errorMessage(e.getMessage())
-                    .stackTrace(Arrays.toString(e.getStackTrace()))
-                    .build();
-            GenericApiResponse<BookmarkQuestionResponseDto> genericApiResponse = ApiResponseBuilder.buildErrorResponse(
-                    BookmarkQuestionResponseDto.class,
-                    "An error occurred while deleting the bookmark",
-                    HttpStatus.NOT_FOUND.value(),
-                    errorResponse
-            );
-            return buildResponse(genericApiResponse, HttpStatus.NOT_FOUND);
+        } catch (NoSuchElementException e) {
+            return ExceptionResponseHandler.NoSuchElementException(e);
         } catch (UnauthorizedAccessException e) {
             return ExceptionResponseHandler.UnauthorizedAccessException(e);
         }
diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Exceptions/ExceptionResponseHandler.java b/backend/src/main/java/com/group1/programminglanguagesforum/Exceptions/ExceptionResponseHandler.java
index bf941861..391358c5 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Exceptions/ExceptionResponseHandler.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Exceptions/ExceptionResponseHandler.java
@@ -120,7 +120,7 @@ public static <T> ResponseEntity<GenericApiResponse<T>> EntityExistsException(En
         GenericApiResponse<T> response = ApiResponseBuilder.buildErrorResponse(
                 UserProfileResponseDto.class,
                 e.getMessage(),
-                HttpStatus.CONFLICT.value(),
+                HttpStatus.BAD_REQUEST.value(),
                 errorResponse
         );
 
diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Services/BookmarkService.java b/backend/src/main/java/com/group1/programminglanguagesforum/Services/BookmarkService.java
index c08fd12c..b33beb04 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Services/BookmarkService.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Services/BookmarkService.java
@@ -8,6 +8,7 @@
 import com.group1.programminglanguagesforum.Exceptions.UnauthorizedAccessException;
 import com.group1.programminglanguagesforum.Repositories.BookmarkRepository;
 
+import jakarta.persistence.EntityExistsException;
 import lombok.RequiredArgsConstructor;
 
 import org.modelmapper.ModelMapper;
@@ -30,7 +31,11 @@ public BookmarkQuestionResponseDto bookmarkQuestion(Long questionId) throws Unau
         User user = userContextService.getCurrentUser();
         
         Optional<Question> question = questionService.findById(questionId);
-        Question questionEntity = question.orElseThrow();
+        Question questionEntity = question.orElseThrow(() -> new NoSuchElementException("Question not found"));
+
+        bookmarkRepository.findByUserAndQuestion(user, questionEntity).ifPresent(bookmark -> {
+            throw new EntityExistsException("Question already bookmarked");
+        });
         
         Bookmark bookmark = Bookmark.builder()
                 .user(user)
@@ -45,8 +50,8 @@ public BookmarkQuestionResponseDto bookmarkQuestion(Long questionId) throws Unau
 
     public BookmarkQuestionResponseDto removeBookmark(Long questionId) throws UnauthorizedAccessException {
         User user = userContextService.getCurrentUser();
-        Question question = questionService.findById(questionId).orElseThrow();
-        Bookmark bookmark = bookmarkRepository.findByUserAndQuestion(user, question).orElseThrow(NoSuchElementException::new);
+        Question question = questionService.findById(questionId).orElseThrow(() -> new NoSuchElementException("Question not found"));
+        Bookmark bookmark = bookmarkRepository.findByUserAndQuestion(user, question).orElseThrow(() -> new NoSuchElementException("Bookmark not found"));
 
         bookmarkRepository.delete(bookmark);
 
diff --git a/swagger/openapi.yml b/swagger/openapi.yml
index 1f2498cd..88b152ea 100644
--- a/swagger/openapi.yml
+++ b/swagger/openapi.yml
@@ -551,6 +551,8 @@ paths:
       responses:
         "200":
           description: Question successfully bookmarked
+        "400":
+          $ref: "#/components/responses/BadRequestResponse"
         "401":
           $ref: "#/components/responses/UnauthorizedResponse"
         "404":