How long does a Microsoft 365 tenant-to-tenant migration take?

Three to nine months for a mid-sized organisation, covering discovery and design, identity and domain planning, mailbox and file migration in waves, Teams and SharePoint migration, device re-enrolment, and cutover. Small tenants move faster; the domain move — which requires a real cutover window — is the fixed constraint no tooling removes entirely.

What actually gates the timeline

• Domain verification: a domain must leave the source tenant before the target can verify it, forcing a cutover window.
• Teams and SharePoint migration is usually the hardest and slowest part, not mailboxes.
• Entra configuration, Conditional Access, Intune policies, app registrations, and licences don't migrate — they're rebuilt in the target tenant, and that rebuild work often takes longer than the data moves.

Shrinking the cutover window

• Microsoft's cross-tenant mailbox and OneDrive migration tooling, plus careful MX record sequencing, can shrink the domain-down window to hours rather than days.