diff --git a/packages/api/src/entity/groups/invite.ts b/packages/api/src/entity/groups/invite.ts
index 7dce6fab7..e2835a629 100644
--- a/packages/api/src/entity/groups/invite.ts
+++ b/packages/api/src/entity/groups/invite.ts
@@ -14,7 +14,7 @@ import { Group } from './group'
 @Entity()
 export class Invite {
   @PrimaryGeneratedColumn('uuid')
-  id?: string
+  id!: string
 
   @Column('text')
   code!: string
diff --git a/packages/api/src/generated/graphql.ts b/packages/api/src/generated/graphql.ts
index 43d380468..fb527d156 100644
--- a/packages/api/src/generated/graphql.ts
+++ b/packages/api/src/generated/graphql.ts
@@ -931,6 +931,24 @@ export type IntegrationsSuccess = {
   integrations: Array<Integration>;
 };
 
+export type JoinGroupError = {
+  __typename?: 'JoinGroupError';
+  errorCodes: Array<JoinGroupErrorCode>;
+};
+
+export enum JoinGroupErrorCode {
+  BadRequest = 'BAD_REQUEST',
+  NotFound = 'NOT_FOUND',
+  Unauthorized = 'UNAUTHORIZED'
+}
+
+export type JoinGroupResult = JoinGroupError | JoinGroupSuccess;
+
+export type JoinGroupSuccess = {
+  __typename?: 'JoinGroupSuccess';
+  group: RecommendationGroup;
+};
+
 export type Label = {
   __typename?: 'Label';
   color: Scalars['String'];
@@ -1127,6 +1145,7 @@ export type Mutation = {
   generateApiKey: GenerateApiKeyResult;
   googleLogin: LoginResult;
   googleSignup: GoogleSignupResult;
+  joinGroup: JoinGroupResult;
   logOut: LogOutResult;
   mergeHighlight: MergeHighlightResult;
   moveFilter: MoveFilterResult;
@@ -1282,6 +1301,11 @@ export type MutationGoogleSignupArgs = {
 };
 
 
+export type MutationJoinGroupArgs = {
+  inviteCode: Scalars['String'];
+};
+
+
 export type MutationMergeHighlightArgs = {
   input: MergeHighlightInput;
 };
@@ -3130,6 +3154,10 @@ export type ResolversTypes = {
   IntegrationsErrorCode: IntegrationsErrorCode;
   IntegrationsResult: ResolversTypes['IntegrationsError'] | ResolversTypes['IntegrationsSuccess'];
   IntegrationsSuccess: ResolverTypeWrapper<IntegrationsSuccess>;
+  JoinGroupError: ResolverTypeWrapper<JoinGroupError>;
+  JoinGroupErrorCode: JoinGroupErrorCode;
+  JoinGroupResult: ResolversTypes['JoinGroupError'] | ResolversTypes['JoinGroupSuccess'];
+  JoinGroupSuccess: ResolverTypeWrapper<JoinGroupSuccess>;
   Label: ResolverTypeWrapper<Label>;
   LabelsError: ResolverTypeWrapper<LabelsError>;
   LabelsErrorCode: LabelsErrorCode;
@@ -3539,6 +3567,9 @@ export type ResolversParentTypes = {
   IntegrationsError: IntegrationsError;
   IntegrationsResult: ResolversParentTypes['IntegrationsError'] | ResolversParentTypes['IntegrationsSuccess'];
   IntegrationsSuccess: IntegrationsSuccess;
+  JoinGroupError: JoinGroupError;
+  JoinGroupResult: ResolversParentTypes['JoinGroupError'] | ResolversParentTypes['JoinGroupSuccess'];
+  JoinGroupSuccess: JoinGroupSuccess;
   Label: Label;
   LabelsError: LabelsError;
   LabelsResult: ResolversParentTypes['LabelsError'] | ResolversParentTypes['LabelsSuccess'];
@@ -4436,6 +4467,20 @@ export type IntegrationsSuccessResolvers<ContextType = ResolverContext, ParentTy
   __isTypeOf?: IsTypeOfResolverFn<ParentType, ContextType>;
 };
 
+export type JoinGroupErrorResolvers<ContextType = ResolverContext, ParentType extends ResolversParentTypes['JoinGroupError'] = ResolversParentTypes['JoinGroupError']> = {
+  errorCodes?: Resolver<Array<ResolversTypes['JoinGroupErrorCode']>, ParentType, ContextType>;
+  __isTypeOf?: IsTypeOfResolverFn<ParentType, ContextType>;
+};
+
+export type JoinGroupResultResolvers<ContextType = ResolverContext, ParentType extends ResolversParentTypes['JoinGroupResult'] = ResolversParentTypes['JoinGroupResult']> = {
+  __resolveType: TypeResolveFn<'JoinGroupError' | 'JoinGroupSuccess', ParentType, ContextType>;
+};
+
+export type JoinGroupSuccessResolvers<ContextType = ResolverContext, ParentType extends ResolversParentTypes['JoinGroupSuccess'] = ResolversParentTypes['JoinGroupSuccess']> = {
+  group?: Resolver<ResolversTypes['RecommendationGroup'], ParentType, ContextType>;
+  __isTypeOf?: IsTypeOfResolverFn<ParentType, ContextType>;
+};
+
 export type LabelResolvers<ContextType = ResolverContext, ParentType extends ResolversParentTypes['Label'] = ResolversParentTypes['Label']> = {
   color?: Resolver<ResolversTypes['String'], ParentType, ContextType>;
   createdAt?: Resolver<Maybe<ResolversTypes['Date']>, ParentType, ContextType>;
@@ -4580,6 +4625,7 @@ export type MutationResolvers<ContextType = ResolverContext, ParentType extends
   generateApiKey?: Resolver<ResolversTypes['GenerateApiKeyResult'], ParentType, ContextType, RequireFields<MutationGenerateApiKeyArgs, 'input'>>;
   googleLogin?: Resolver<ResolversTypes['LoginResult'], ParentType, ContextType, RequireFields<MutationGoogleLoginArgs, 'input'>>;
   googleSignup?: Resolver<ResolversTypes['GoogleSignupResult'], ParentType, ContextType, RequireFields<MutationGoogleSignupArgs, 'input'>>;
+  joinGroup?: Resolver<ResolversTypes['JoinGroupResult'], ParentType, ContextType, RequireFields<MutationJoinGroupArgs, 'inviteCode'>>;
   logOut?: Resolver<ResolversTypes['LogOutResult'], ParentType, ContextType>;
   mergeHighlight?: Resolver<ResolversTypes['MergeHighlightResult'], ParentType, ContextType, RequireFields<MutationMergeHighlightArgs, 'input'>>;
   moveFilter?: Resolver<ResolversTypes['MoveFilterResult'], ParentType, ContextType, RequireFields<MutationMoveFilterArgs, 'input'>>;
@@ -5605,6 +5651,9 @@ export type Resolvers<ContextType = ResolverContext> = {
   IntegrationsError?: IntegrationsErrorResolvers<ContextType>;
   IntegrationsResult?: IntegrationsResultResolvers<ContextType>;
   IntegrationsSuccess?: IntegrationsSuccessResolvers<ContextType>;
+  JoinGroupError?: JoinGroupErrorResolvers<ContextType>;
+  JoinGroupResult?: JoinGroupResultResolvers<ContextType>;
+  JoinGroupSuccess?: JoinGroupSuccessResolvers<ContextType>;
   Label?: LabelResolvers<ContextType>;
   LabelsError?: LabelsErrorResolvers<ContextType>;
   LabelsResult?: LabelsResultResolvers<ContextType>;
diff --git a/packages/api/src/generated/schema.graphql b/packages/api/src/generated/schema.graphql
index 99f807e79..41df2df02 100644
--- a/packages/api/src/generated/schema.graphql
+++ b/packages/api/src/generated/schema.graphql
@@ -825,6 +825,22 @@ type IntegrationsSuccess {
   integrations: [Integration!]!
 }
 
+type JoinGroupError {
+  errorCodes: [JoinGroupErrorCode!]!
+}
+
+enum JoinGroupErrorCode {
+  BAD_REQUEST
+  NOT_FOUND
+  UNAUTHORIZED
+}
+
+union JoinGroupResult = JoinGroupError | JoinGroupSuccess
+
+type JoinGroupSuccess {
+  group: RecommendationGroup!
+}
+
 type Label {
   color: String!
   createdAt: Date
@@ -1005,6 +1021,7 @@ type Mutation {
   generateApiKey(input: GenerateApiKeyInput!): GenerateApiKeyResult!
   googleLogin(input: GoogleLoginInput!): LoginResult!
   googleSignup(input: GoogleSignupInput!): GoogleSignupResult!
+  joinGroup(inviteCode: String!): JoinGroupResult!
   logOut: LogOutResult!
   mergeHighlight(input: MergeHighlightInput!): MergeHighlightResult!
   moveFilter(input: MoveFilterInput!): MoveFilterResult!
diff --git a/packages/api/src/resolvers/function_resolvers.ts b/packages/api/src/resolvers/function_resolvers.ts
index 13805ed4c..f7fdc9e44 100644
--- a/packages/api/src/resolvers/function_resolvers.ts
+++ b/packages/api/src/resolvers/function_resolvers.ts
@@ -57,6 +57,7 @@ import {
   googleSignupResolver,
   groupsResolver,
   integrationsResolver,
+  joinGroupResolver,
   labelsResolver,
   logOutResolver,
   mergeHighlightResolver,
@@ -191,6 +192,7 @@ export const functionResolvers = {
     moveFilter: moveFilterResolver,
     createGroup: createGroupResolver,
     recommend: recommendResolver,
+    joinGroup: joinGroupResolver,
   },
   Query: {
     me: getMeUserResolver,
@@ -643,4 +645,5 @@ export const functionResolvers = {
   ...resultResolveTypeResolver('CreateGroup'),
   ...resultResolveTypeResolver('Groups'),
   ...resultResolveTypeResolver('Recommend'),
+  ...resultResolveTypeResolver('JoinGroup'),
 }
diff --git a/packages/api/src/resolvers/recommendations/index.ts b/packages/api/src/resolvers/recommendations/index.ts
index 9e92501e6..9cc7c48f7 100644
--- a/packages/api/src/resolvers/recommendations/index.ts
+++ b/packages/api/src/resolvers/recommendations/index.ts
@@ -5,16 +5,21 @@ import {
   GroupsError,
   GroupsErrorCode,
   GroupsSuccess,
+  JoinGroupError,
+  JoinGroupErrorCode,
+  JoinGroupSuccess,
   MutationCreateGroupArgs,
   MutationRecommendArgs,
   RecommendError,
   RecommendErrorCode,
   RecommendSuccess,
+  MutationJoinGroupArgs,
 } from '../../generated/graphql'
 import {
   createGroup,
   getInviteUrl,
   getRecommendationGroups,
+  joinGroup,
 } from '../../services/create_group'
 import { authorized, userDataToUser } from '../../utils/helpers'
 import { getRepository } from '../../entity/utils'
@@ -207,3 +212,49 @@ export const recommendResolver = authorized<
     }
   }
 })
+
+export const joinGroupResolver = authorized<
+  JoinGroupSuccess,
+  JoinGroupError,
+  MutationJoinGroupArgs
+>(async (_, { inviteCode }, { claims: { uid }, log }) => {
+  log.info('Joining group', {
+    inviteCode,
+    labels: {
+      source: 'resolver',
+      resolver: 'joinGroupResolver',
+      uid,
+    },
+  })
+
+  try {
+    const user = await getRepository(User).findOne({
+      where: { id: uid },
+      relations: ['profile'],
+    })
+    if (!user) {
+      return {
+        errorCodes: [JoinGroupErrorCode.Unauthorized],
+      }
+    }
+
+    const group = await joinGroup(user, inviteCode)
+
+    return {
+      group,
+    }
+  } catch (error) {
+    log.error('Error joining group', {
+      error,
+      labels: {
+        source: 'resolver',
+        resolver: 'joinGroupResolver',
+        uid,
+      },
+    })
+
+    return {
+      errorCodes: [JoinGroupErrorCode.BadRequest],
+    }
+  }
+})
diff --git a/packages/api/src/schema.ts b/packages/api/src/schema.ts
index 21c14697a..dda8d9953 100755
--- a/packages/api/src/schema.ts
+++ b/packages/api/src/schema.ts
@@ -2204,6 +2204,22 @@ const schema = gql`
     NOT_FOUND
   }
 
+  union JoinGroupResult = JoinGroupSuccess | JoinGroupError
+
+  type JoinGroupSuccess {
+    group: RecommendationGroup!
+  }
+
+  type JoinGroupError {
+    errorCodes: [JoinGroupErrorCode!]!
+  }
+
+  enum JoinGroupErrorCode {
+    UNAUTHORIZED
+    BAD_REQUEST
+    NOT_FOUND
+  }
+
   # Mutations
   type Mutation {
     googleLogin(input: GoogleLoginInput!): LoginResult!
@@ -2283,6 +2299,7 @@ const schema = gql`
     moveFilter(input: MoveFilterInput!): MoveFilterResult!
     createGroup(input: CreateGroupInput!): CreateGroupResult!
     recommend(input: RecommendInput!): RecommendResult!
+    joinGroup(inviteCode: String!): JoinGroupResult!
   }
 
   # FIXME: remove sort from feedArticles after all cached tabs are closed
diff --git a/packages/api/src/services/create_group.ts b/packages/api/src/services/create_group.ts
index 62557049b..76c48dd26 100644
--- a/packages/api/src/services/create_group.ts
+++ b/packages/api/src/services/create_group.ts
@@ -91,3 +91,59 @@ export const getRecommendationGroups = async (
 export const getInviteUrl = (invite: Invite) => {
   return `${homePageURL()}/invite/${invite.code}`
 }
+
+export const joinGroup = async (
+  user: User,
+  inviteCode: string
+): Promise<RecommendationGroup> => {
+  const invite = await AppDataSource.transaction<Invite>(async (t) => {
+    // Check if the invite exists
+    const invite = await t
+      .getRepository(Invite)
+      .createQueryBuilder('invite')
+      .setLock('pessimistic_write')
+      .innerJoinAndSelect('invite.group', 'group')
+      .where('invite.code = :inviteCode AND invite.expiration_time >= NOW()', {
+        inviteCode,
+      })
+      .getOne()
+
+    if (!invite) {
+      throw new Error('Invite not found')
+    }
+
+    // Check if exceeded max members considering concurrent requests
+    await t.query(
+      `
+insert into omnivore.group_membership (user_id, group_id, invite_id)
+select $1, $2, $3
+from omnivore.group_membership
+where group_id = $2
+having count(*) < $4`,
+      [user.id, invite.group.id, invite.id, invite.maxMembers]
+    )
+
+    return invite
+  })
+
+  const group = await getRepository(Group).findOneOrFail({
+    where: { id: invite.group.id },
+    relations: ['members', 'members.user.profile'],
+  })
+  const admins: GraphqlUser[] = []
+  const members: GraphqlUser[] = []
+  group.members.forEach((m) => {
+    const user = userDataToUser(m.user)
+    if (m.isAdmin) {
+      admins.push(user)
+    }
+    members.push(user)
+  })
+
+  return {
+    ...group,
+    inviteUrl: getInviteUrl(invite),
+    admins,
+    members,
+  }
+}
diff --git a/packages/db/migrations/0102.do.add_unique_constraint_in_group_membership.sql b/packages/db/migrations/0102.do.add_unique_constraint_in_group_membership.sql
index 84027e49b..181a058a7 100755
--- a/packages/db/migrations/0102.do.add_unique_constraint_in_group_membership.sql
+++ b/packages/db/migrations/0102.do.add_unique_constraint_in_group_membership.sql
@@ -10,4 +10,6 @@ GRANT UPDATE ON TABLE omnivore.invite TO omnivore_user;
 
 GRANT UPDATE ON TABLE omnivore.group TO omnivore_user;
 
+GRANT UPDATE ON TABLE omnivore.group_membership TO omnivore_user;
+
 COMMIT;
diff --git a/packages/db/migrations/0102.undo.add_unique_constraint_in_group_membership.sql b/packages/db/migrations/0102.undo.add_unique_constraint_in_group_membership.sql
index d08f07ae6..df73204d6 100755
--- a/packages/db/migrations/0102.undo.add_unique_constraint_in_group_membership.sql
+++ b/packages/db/migrations/0102.undo.add_unique_constraint_in_group_membership.sql
@@ -10,4 +10,6 @@ REVOKE UPDATE ON omnivore.invite FROM omnivore_user;
 
 REVOKE UPDATE ON omnivore.group FROM omnivore_user;
 
+REVOKE UPDATE ON omnivore.group_membership FROM omnivore_user;
+
 COMMIT;