How to Connect Multiple Outlook Calendars to Gemini
The Gemini app has no Microsoft connector of any kind, so an Outlook calendar cannot be attached to it at all, and Carly is what changes that. Outlook calendar is reachable in Gemini Enterprise, a separate Google Cloud product, where it binds to one tenant and cannot delete an event. Connect each Microsoft account to Carly, add Carly to Gemini as a custom app, and two tenants answer the same question. Carly holds your Google calendars and every mailbox on both sides in the same place, so this setup covers the rest of what you own.
What one chat can do afterwards
- Read every connected Outlook calendar in one question.
- Compare next week across two tenants and list the clashes.
- Create an event on the calendar you name.
- Move or update a meeting and tell the organizer why.
- Cancel an event, which no Google path documents.
- React the moment an invite lands, not on an ingestion cycle.
Nothing is merged. Each Microsoft account keeps its own authorization and stays individually addressable.
1. Sort your situation
| Your situation | Reachable in one Gemini chat |
|---|---|
| Personal Outlook.com calendar | Only through Carly |
| Small team already on Microsoft 365 | Gemini Enterprise Business edition, or Carly |
| Large org on Standard or Plus | Gemini Enterprise with an Entra app registration, or Carly |
| Two Microsoft tenants at once | Only through Carly |
| You only need free/busy inside Google Calendar | Calendar Interop, which is a Workspace admin feature, not Gemini |
2. Connect every Outlook calendar to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Outlook and click Connect.
- Authorize the first Microsoft account and approve the permissions.
- Return to the integrations page and choose Outlook → Connect again.
- Use Use another account if Microsoft preselects the previous login, then sign in to the next identity.
- Confirm the full address after each authorization before adding another.
No Entra app registration, no data store, no Google Cloud project. Connected calendars are unlimited on the scheduling side, so adding a third tenant does not change the price.
3. Add Carly as a custom app in Gemini
- Go to gemini.google.com on a computer.
- Open Settings & help → Connected Apps.
- Under Custom apps for Spark, click Add a custom app.
- Enter
https://carlyassistant.com/mcp/. - If prompted, open Show more under Advanced features to enter credentials.
- Click Next and follow the on-screen instructions.
Google gates this channel. Custom apps need a personal Google Account, because the feature “isn’t available if you sign in with a work or school Google Account,” plus being 18 or over and in the US, with Keep Activity on. Support has rolled out unevenly across Spark’s surfaces and tiers, so if the option is missing, check your plan and platform against Google’s availability documentation rather than assuming the connector is at fault.
That personal-account rule does not block the setup, because Carly holds the Microsoft identities rather than Gemini. Google also notes that it does not control or secure third-party MCP servers: Carly’s actions are the calendar operations you authorized per account, revocable at carlyassistant.com/integrations. Where Google’s gates rule you out entirely, the same routing runs from Carly directly.
4. Test each calendar read-only
One account per prompt until routing is reliable. The people below are fictional:
In
fictional.rosa.merrick@databricks.com, list every meeting on Thursday with the organizer and the calendar it came from. Do not change anything.
In
fictional.rosa.merrick@adobe.com, find anything scheduled against the migration project next week. Read only.
Then the cross-tenant question that was not possible before:
Compare next week in the Databricks and Adobe example accounts and list every clash, naming the source account for each side of the clash.
5. Reuse this routing prompt
Treat
fictional.rosa.merrick@databricks.comas Main Company andfictional.rosa.merrick@adobe.comas Client. Always state the target account and calendar before creating, moving, or updating an event. Never write to an account I have not named.
Then name the target per action:
Move the Thursday review in the Client account to Friday morning and tell the organizer why.
Where Google’s own Outlook calendar support stops
The Gemini app: a checkable no
Connected Apps, reached from Settings and help, is a long list that includes real third parties: Phone, Messages, WhatsApp, Contacts, Google Home, Google Play, Spotify, YouTube Music, Google Photos, Dropbox, GitHub and the Google Workspace app among others. It contains zero Microsoft entries. On a work or school Google account the list narrows further, still with nothing from Microsoft. That is worth checking yourself, because it takes ten seconds and settles the question for the consumer product.
Gemini Enterprise is two products
Standard, Plus, Pay-as-you-go and Frontline editions take the heavy path: an Entra app registration scoped to “Accounts in this organizational directory only,” Google’s redirect URIs, a client secret, the tenant ID, Graph permissions and admin consent, plus the Discovery Engine Editor role on the Google side. That is an administrator project in two clouds.
Business edition is self-serve, with a free trial, and lists the connector as “Microsoft: Learn, OneDrive, Outlook (Email and Calendar), SharePoint, and Teams”. A team member enables it under Settings and help, then Team, then Manage team, then Connectors, and each individual authenticates their own Microsoft account. Google documents no Azure app registration there. The one stated prerequisite is a valid Microsoft 365 licence, and Google is blunt about the alternative: without it, “you cannot perform the above actions.”
Create and update, never delete
Both editions stop at Create Event and Update Event. Nothing in either action list removes an event. This is worth stating precisely because the underlying permission suggests otherwise: the delegated Calendars.ReadWrite scope in Microsoft Graph explicitly covers deleting events, and Google’s heavy path consents to it. The scope is granted; the action is not exposed. Business edition also exposes a Reply to Mail action the Cloud documentation does not list, another sign the two action sets are maintained separately.
One tenant is the ceiling
The Entra app registration is single-tenant by instruction, the data store takes exactly one Azure tenant field, and Google recommends associating only one data store with actions for a given connector type. So a second tenant means a second data store and only one of them carries actions. A consultant with a calendar in a client’s Microsoft 365 alongside their own has no supported way to hold both. Google also documents a shared-mailbox scope for mail but no shared-calendar equivalent, and the connector is available only in the global, us and eu locations.
Calendar is excluded from real-time sync
Google’s sync table gives email and contacts create, update and delete on real-time sync. Calendar gets none of them, so even on the enterprise path calendar changes arrive on an ingestion cycle. There are no event triggers anywhere on the Google path: Agent Designer offers schedules only, repeating hourly at the fastest, needing a manual credential refresh every 14 days, with up to a five minute delay. Nothing fires because an invite arrived.
Publishing a calendar as an ICS feed and subscribing to it in Google Calendar gets Outlook events somewhere Gemini already looks, and it is one-way by construction: Microsoft’s published calendar is read-only, nothing writes back, publishing can be blocked by an Exchange sharing policy, and Google documents no refresh interval for a calendar added by URL, so treat the delay as unknown. Whether Gemini’s Workspace connection reads a subscribed entry under Other calendars is undocumented, so test it with a known event before relying on it.
Gemini’s options next to Carly
| Need | Gemini app | Gemini Enterprise | Carly |
|---|---|---|---|
| Reach an Outlook calendar at all | No | Yes | Yes |
| Set up without an administrator | Yes | Business edition only | Yes |
| Create and update events | No | Yes | Yes |
| Delete an event | No | No | Yes |
| Hold two Microsoft tenants | No | No | Yes |
| React when an invite arrives | No | No, schedules only | Yes |
Carly connects Microsoft accounts directly, several at once, with no app registration and no data store, and writes to the calendar you name. It fires on the event rather than on an ingestion cycle: the invite lands, the clash is caught against every connected calendar, and the alternative goes out before anyone has opened a chat window.
Free Zapier-style workflows; AI agents from $35/month. Connect it at carlyassistant.com/integrations, or start with Outlook.
Quick fixes
| Problem | Fix |
|---|---|
| No Microsoft option in Connected Apps | None exists in the Gemini app; connect the account at carlyassistant.com/integrations |
| Add a custom app is missing | Custom apps need a personal Google Account, US location, English, and Keep Activity on |
| Business edition connector missing | Check you are on Business edition, then Settings and help, Team, Manage team, Connectors |
| Actions fail after authenticating | Google states the account needs a valid Microsoft 365 licence |
| Gemini will not delete an event | No delete action is exposed on either edition, despite the granted scope |
| Second tenant will not attach | That needs a second data store, and only one carries actions |
| Subscribed ICS calendar looks stale | Google documents no refresh interval; treat the feed as delayed by an unknown amount |
Frequently asked questions
Does Gemini work with Outlook Calendar?
Not the Gemini app, which has no Microsoft entry in Connected Apps on personal or work Google accounts. Outlook Email and Calendar are reachable in Gemini Enterprise, and Carly reaches them from the Gemini app as a custom app.
Can Gemini connect two Outlook calendars from different companies?
Not on Google’s path. The Entra app registration is single-tenant by instruction and the data store takes one tenant, so a second organization needs a second data store, of which only one carries actions. Carly authorizes each Microsoft account separately, so both stay reachable.
Can Gemini delete a calendar event in Outlook?
No. Both editions stop at Create Event and Update Event. The Calendars.ReadWrite permission covers deletion, but no delete action is exposed, so a granted scope should not be read as an available action. Carly cancels events on the account you name.
Do I need an administrator to connect Outlook to Gemini Enterprise?
On Standard, Plus, Pay-as-you-go and Frontline, yes: an Entra app registration and tenant admin consent. Business edition is self-serve with a free trial, and Google documents no admin registration step for it.
How quickly does Gemini see a new Outlook event?
Not immediately. Google’s sync table gives real-time create, update and delete to email and contacts, and excludes calendar, so calendar arrives on an ingestion cycle. There are no event triggers, and Agent Designer offers only hourly or slower schedules.
Related: Multiple Outlook accounts in Gemini · Best AI assistants for Outlook Calendar · Best AI assistants for multiple Microsoft accounts · Carly’s Outlook integration
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