diff --git a/packages/backend/src/core/NoteCreateService.ts b/packages/backend/src/core/NoteCreateService.ts
index d8615e7f61bb..02d204641871 100644
--- a/packages/backend/src/core/NoteCreateService.ts
+++ b/packages/backend/src/core/NoteCreateService.ts
@@ -378,8 +378,8 @@ export class NoteCreateService implements OnApplicationShutdown {
 			}
 		}
 
-		if (mentionedUsers.length > (await this.roleService.getUserPolicies(user.id)).mentionLimit) {
-			throw new Error('Too many mentions');
+		if (mentionedUsers.length > 0 && mentionedUsers.length > (await this.roleService.getUserPolicies(user.id)).mentionLimit) {
+			throw new IdentifiableError('9f466dab-c856-48cd-9e65-ff90ff750580', 'Note contains too many mentions');
 		}
 
 		const note = await this.insertNote(user, data, tags, emojis, mentionedUsers);
diff --git a/packages/backend/src/server/api/endpoints/notes/create.ts b/packages/backend/src/server/api/endpoints/notes/create.ts
index 2fa0bd099fe7..2a91d125f215 100644
--- a/packages/backend/src/server/api/endpoints/notes/create.ts
+++ b/packages/backend/src/server/api/endpoints/notes/create.ts
@@ -120,6 +120,12 @@ export const meta = {
 			code: 'CONTAINS_PROHIBITED_WORDS',
 			id: 'aa6e01d3-a85c-669d-758a-76aab43af334',
 		},
+
+		containsTooManyMentions: {
+			message: 'Cannot post because it exceeds the allowed number of mentions.'
+			code: 'CONTAINS_TOO_MANY_MENTIONS',
+			id: '4de0363a-3046-481b-9b0f-feff3e211025',
+		},
 	},
 } as const;
 
@@ -378,9 +384,12 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			} catch (e) {
 				// TODO: 他のErrorもここでキャッチしてエラーメッセージを当てるようにしたい
 				if (e instanceof IdentifiableError) {
-					if (e.id === '689ee33f-f97c-479a-ac49-1b9f8140af99') throw new ApiError(meta.errors.containsProhibitedWords);
+					if (e.id === '689ee33f-f97c-479a-ac49-1b9f8140af99') {
+						throw new ApiError(meta.errors.containsProhibitedWords);
+					} else if (e.id === '9f466dab-c856-48cd-9e65-ff90ff750580') {
+						throw new ApiError(meta.errors.containsTooManyMentions);
+					}
 				}
-
 				throw e;
 			}
 		});