diff --git a/packages/backend/src/server/api/endpoints/admin/roles/users.ts b/packages/backend/src/server/api/endpoints/admin/roles/users.ts
index 35edca5460..328c0bb91b 100644
--- a/packages/backend/src/server/api/endpoints/admin/roles/users.ts
+++ b/packages/backend/src/server/api/endpoints/admin/roles/users.ts
@@ -28,6 +28,7 @@ export const paramDef = {
 		roleId: { type: 'string', format: 'misskey:id' },
 		sinceId: { type: 'string', format: 'misskey:id' },
 		untilId: { type: 'string', format: 'misskey:id' },
+		userId: { type: 'string', format: 'misskey:id' },
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
 	},
 	required: ['roleId'],
@@ -63,6 +64,10 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 				}))
 				.innerJoinAndSelect('assign.user', 'user');
 
+			if (ps.userId != null) {
+				query.andWhere('assign.userId = :userId', { userId: ps.userId });
+			}
+
 			const assigns = await query
 				.take(ps.limit)
 				.getMany();