Can I migrate from Google Workspace to Microsoft 365 without downtime?

Not with zero disruption, but close. Mailbox and file content can be migrated ahead of time while Google Workspace stays live, so the actual cutover is just the MX record change and final delta sync — typically a window of minutes to a few hours, scheduled outside working hours, rather than a multi-day blackout.

The staged approach

• Migrate the bulk of mail, calendar, and Drive content in advance using a migration tool while users keep working in Google Workspace.
• Run delta syncs to catch up on new mail as the cutover date approaches.
• Change MX and other DNS records last, once final delta syncs are scheduled — this is the only step users actually notice.
• Communicate the cutover window clearly; Outlook and Teams client rollout is easier done in the days just before, not during, the mail cutover.