diff --git a/packages/backend/src/server/api/mastodon/endpoints/list.ts b/packages/backend/src/server/api/mastodon/endpoints/list.ts
index ad4641db5..e56e67846 100644
--- a/packages/backend/src/server/api/mastodon/endpoints/list.ts
+++ b/packages/backend/src/server/api/mastodon/endpoints/list.ts
@@ -8,6 +8,8 @@ import { ListHelpers } from "@/server/api/mastodon/helpers/list.js";
 import { UserConverter } from "@/server/api/mastodon/converters/user.js";
 import { PaginationHelpers } from "@/server/api/mastodon/helpers/pagination.js";
 import { UserLists } from "@/models/index.js";
+import { NoteHelpers } from "@/server/api/mastodon/helpers/note.js";
+import { getUser } from "@/server/api/common/getters.js";
 
 export function setupEndpointsList(router: Router): void {
     router.get("/v1/lists", async (ctx, reply) => {
@@ -138,22 +140,37 @@ export function setupEndpointsList(router: Router): void {
     router.post<{ Params: { id: string } }>(
         "/v1/lists/:id/accounts",
         async (ctx, reply) => {
-            const BASE_URL = `${ctx.protocol}://${ctx.hostname}`;
-            const accessTokens = ctx.headers.authorization;
-            const client = getClient(BASE_URL, accessTokens);
             try {
-                const data = await client.addAccountsToList(
-                    convertId(ctx.params.id, IdType.IceshrimpId),
-                    (ctx.query.account_ids as string[]).map((id) =>
-                        convertId(id, IdType.IceshrimpId),
-                    ),
-                );
-                ctx.body = data.data;
+                const auth = await authenticate(ctx.headers.authorization, null);
+                const user = auth[0] ?? undefined;
+
+                if (!user) {
+                    ctx.status = 401;
+                    return;
+                }
+
+                const id = convertId(ctx.params.id, IdType.IceshrimpId);
+                const list = await UserLists.findOneBy({userId: user.id, id: id});
+
+                if (!list) {
+                    ctx.status = 404;
+                    return;
+                }
+
+                const body = ctx.request.body as any;
+                if (!body['account_ids']) {
+                    ctx.status = 400;
+                    ctx.body = { error: "Missing account_ids[] field" };
+                    return;
+                }
+
+                const ids = NoteHelpers.normalizeToArray(body['account_ids']).map(p => convertId(p, IdType.IceshrimpId));
+                const targets = await Promise.all(ids.map(p => getUser(p)));
+                await ListHelpers.addToList(user, list, targets);
+                ctx.body = {}
             } catch (e: any) {
-                console.error(e);
-                console.error(e.response.data);
-                ctx.status = 401;
-                ctx.body = e.response.data;
+                ctx.status = 400;
+                ctx.body = { error: e.message };
             }
         },
     );
diff --git a/packages/backend/src/server/api/mastodon/helpers/list.ts b/packages/backend/src/server/api/mastodon/helpers/list.ts
index 4513a1c1f..85cdb9339 100644
--- a/packages/backend/src/server/api/mastodon/helpers/list.ts
+++ b/packages/backend/src/server/api/mastodon/helpers/list.ts
@@ -1,8 +1,9 @@
 import { ILocalUser, User } from "@/models/entities/user.js";
-import { UserListJoinings, UserLists } from "@/models/index.js";
+import { Blockings, UserListJoinings, UserLists } from "@/models/index.js";
 import { LinkPaginationObject } from "@/server/api/mastodon/helpers/user.js";
 import { PaginationHelpers } from "@/server/api/mastodon/helpers/pagination.js";
 import { UserList } from "@/models/entities/user-list.js";
+import { pushUserToUserList } from "@/services/user-list/push.js";
 
 export class ListHelpers {
     public static async getLists(user: ILocalUser): Promise<MastodonEntity.List[]> {
@@ -53,4 +54,29 @@ export class ListHelpers {
         if (user.id != list.userId) throw new Error("List is not owned by user");
         await UserLists.delete(list.id);
     }
+
+    public static async addToList(localUser: ILocalUser, list: UserList, usersToAdd: User[]) {
+        if (localUser.id != list.userId) throw new Error("List is not owned by user");
+        for (const user of usersToAdd) {
+            if (user.id !== localUser.id) {
+                const isBlocked = await Blockings.exist({
+                    where: {
+                        blockerId: user.id,
+                        blockeeId: localUser.id,
+                    },
+                });
+                if (isBlocked) throw Error("Can't add users you've been blocked by to list");
+            }
+
+            const exist = await UserListJoinings.exist({
+                where: {
+                    userListId: list.id,
+                    userId: user.id,
+                },
+            });
+
+            if (exist) continue;
+            await pushUserToUserList(user, list);
+        }
+    }
 }