diff --git a/packages/workspace/src/Domain/Invite/WorkspaceInviteRepositoryInterface.ts b/packages/workspace/src/Domain/Invite/WorkspaceInviteRepositoryInterface.ts
index 40625a642..6f4848d6f 100644
--- a/packages/workspace/src/Domain/Invite/WorkspaceInviteRepositoryInterface.ts
+++ b/packages/workspace/src/Domain/Invite/WorkspaceInviteRepositoryInterface.ts
@@ -1,5 +1,8 @@
+import { Uuid } from '@standardnotes/common'
+
 import { WorkspaceInvite } from './WorkspaceInvite'
 
 export interface WorkspaceInviteRepositoryInterface {
+  findOneByUuid(uuid: Uuid): Promise<WorkspaceInvite | null>
   save(workspace: WorkspaceInvite): Promise<WorkspaceInvite>
 }
diff --git a/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.spec.ts b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.spec.ts
new file mode 100644
index 000000000..145549ba7
--- /dev/null
+++ b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.spec.ts
@@ -0,0 +1,71 @@
+import 'reflect-metadata'
+import { TimerInterface } from '@standardnotes/time'
+
+import { WorkspaceInvite } from '../../Invite/WorkspaceInvite'
+import { WorkspaceInviteRepositoryInterface } from '../../Invite/WorkspaceInviteRepositoryInterface'
+import { WorkspaceUserRepositoryInterface } from '../../Workspace/WorkspaceUserRepositoryInterface'
+
+import { AcceptInvitation } from './AcceptInvitation'
+
+describe('AcceptInvitation', () => {
+  let workspaceInviteRepository: WorkspaceInviteRepositoryInterface
+  let workspaceUserRepository: WorkspaceUserRepositoryInterface
+  let timer: TimerInterface
+  let invite: WorkspaceInvite
+
+  const createUseCase = () => new AcceptInvitation(workspaceInviteRepository, workspaceUserRepository, timer)
+
+  beforeEach(() => {
+    invite = {
+      uuid: 'i-1-2-3',
+      workspaceUuid: 'w-1-2-3',
+    } as jest.Mocked<WorkspaceInvite>
+    workspaceInviteRepository = {} as jest.Mocked<WorkspaceInviteRepositoryInterface>
+    workspaceInviteRepository.findOneByUuid = jest.fn().mockReturnValue(invite)
+    workspaceInviteRepository.save = jest.fn()
+
+    workspaceUserRepository = {} as jest.Mocked<WorkspaceUserRepositoryInterface>
+    workspaceUserRepository.save = jest.fn()
+
+    timer = {} as jest.Mocked<TimerInterface>
+    timer.getTimestampInMicroseconds = jest.fn().mockReturnValue(1)
+  })
+
+  it('should accept an invite and assign user to workspace', async () => {
+    await createUseCase().execute({
+      acceptingUserUuid: 'u-1-2-3',
+      encryptedPrivateKey: 'foo',
+      publicKey: 'bar',
+      invitationUuid: 'i-1-2-3',
+    })
+
+    expect(workspaceInviteRepository.save).toHaveBeenCalledWith({
+      acceptingUserUuid: 'u-1-2-3',
+      status: 'accepted',
+      updatedAt: 1,
+      uuid: 'i-1-2-3',
+      workspaceUuid: 'w-1-2-3',
+    })
+    expect(workspaceUserRepository.save).toHaveBeenCalledWith({
+      encryptedPrivateKey: 'foo',
+      publicKey: 'bar',
+      status: 'pending-keyshare',
+      userUuid: 'u-1-2-3',
+      workspaceUuid: 'w-1-2-3',
+    })
+  })
+
+  it('should not accept an invite if it does not exist', async () => {
+    workspaceInviteRepository.findOneByUuid = jest.fn().mockReturnValue(null)
+
+    await createUseCase().execute({
+      acceptingUserUuid: 'u-1-2-3',
+      encryptedPrivateKey: 'foo',
+      publicKey: 'bar',
+      invitationUuid: 'i-1-2-3',
+    })
+
+    expect(workspaceInviteRepository.save).not.toHaveBeenCalled()
+    expect(workspaceUserRepository.save).not.toHaveBeenCalled()
+  })
+})
diff --git a/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.ts b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.ts
new file mode 100644
index 000000000..0d7514e77
--- /dev/null
+++ b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitation.ts
@@ -0,0 +1,50 @@
+import { TimerInterface } from '@standardnotes/time'
+import { inject, injectable } from 'inversify'
+
+import TYPES from '../../../Bootstrap/Types'
+import { WorkspaceInviteRepositoryInterface } from '../../Invite/WorkspaceInviteRepositoryInterface'
+import { WorkspaceInviteStatus } from '../../Invite/WorkspaceInviteStatus'
+import { WorkspaceUser } from '../../Workspace/WorkspaceUser'
+import { WorkspaceUserRepositoryInterface } from '../../Workspace/WorkspaceUserRepositoryInterface'
+import { WorkspaceUserStatus } from '../../Workspace/WorkspaceUserStatus'
+import { UseCaseInterface } from '../UseCaseInterface'
+
+import { AcceptInvitationDTO } from './AcceptInvitationDTO'
+import { AcceptInvitationResponse } from './AcceptInvitationResponse'
+
+@injectable()
+export class AcceptInvitation implements UseCaseInterface {
+  constructor(
+    @inject(TYPES.WorkspaceInviteRepository) private workspaceInviteRepository: WorkspaceInviteRepositoryInterface,
+    @inject(TYPES.WorkspaceUserRepository) private workspaceUserRepository: WorkspaceUserRepositoryInterface,
+    @inject(TYPES.Timer) private timer: TimerInterface,
+  ) {}
+
+  async execute(dto: AcceptInvitationDTO): Promise<AcceptInvitationResponse> {
+    const invite = await this.workspaceInviteRepository.findOneByUuid(dto.invitationUuid)
+    if (invite === null) {
+      return {
+        success: false,
+      }
+    }
+
+    invite.acceptingUserUuid = dto.acceptingUserUuid
+    invite.updatedAt = this.timer.getTimestampInMicroseconds()
+    invite.status = WorkspaceInviteStatus.Accepted
+
+    await this.workspaceInviteRepository.save(invite)
+
+    const workspaceUser = new WorkspaceUser()
+    workspaceUser.userUuid = dto.acceptingUserUuid
+    workspaceUser.workspaceUuid = invite.workspaceUuid
+    workspaceUser.publicKey = dto.publicKey
+    workspaceUser.encryptedPrivateKey = dto.encryptedPrivateKey
+    workspaceUser.status = WorkspaceUserStatus.PendingKeyshare
+
+    await this.workspaceUserRepository.save(workspaceUser)
+
+    return {
+      success: true,
+    }
+  }
+}
diff --git a/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationDTO.ts b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationDTO.ts
new file mode 100644
index 000000000..b36db28ea
--- /dev/null
+++ b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationDTO.ts
@@ -0,0 +1,8 @@
+import { Uuid } from '@standardnotes/common'
+
+export type AcceptInvitationDTO = {
+  invitationUuid: Uuid
+  acceptingUserUuid: Uuid
+  publicKey: string
+  encryptedPrivateKey: string
+}
diff --git a/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationResponse.ts b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationResponse.ts
new file mode 100644
index 000000000..adf77d586
--- /dev/null
+++ b/packages/workspace/src/Domain/UseCase/AcceptInvitation/AcceptInvitationResponse.ts
@@ -0,0 +1,3 @@
+export type AcceptInvitationResponse = {
+  success: boolean
+}
diff --git a/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.spec.ts b/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.spec.ts
index 60c2c2409..e50ef9b84 100644
--- a/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.spec.ts
+++ b/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.spec.ts
@@ -27,4 +27,13 @@ describe('MySQLWorkspaceInviteRepository', () => {
 
     expect(ormRepository.save).toHaveBeenCalledWith(invite)
   })
+
+  it('should find one by uuid', async () => {
+    queryBuilder.where = jest.fn().mockReturnThis()
+    queryBuilder.getOne = jest.fn().mockReturnValue(null)
+
+    await createRepository().findOneByUuid('i-1-2-3')
+
+    expect(queryBuilder.where).toHaveBeenCalledWith('uuid = :uuid', { uuid: 'i-1-2-3' })
+  })
 })
diff --git a/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.ts b/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.ts
index 9f722f134..d2dde8839 100644
--- a/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.ts
+++ b/packages/workspace/src/Infra/MySQL/MySQLWorkspaceInviteRepository.ts
@@ -12,6 +12,10 @@ export class MySQLWorkspaceInviteRepository implements WorkspaceInviteRepository
     private ormRepository: Repository<WorkspaceInvite>,
   ) {}
 
+  async findOneByUuid(uuid: string): Promise<WorkspaceInvite | null> {
+    return this.ormRepository.createQueryBuilder().where('uuid = :uuid', { uuid }).getOne()
+  }
+
   async save(workspaceInvite: WorkspaceInvite): Promise<WorkspaceInvite> {
     return this.ormRepository.save(workspaceInvite)
   }