How to Connect Slack and Microsoft Teams - Full Integration Guide
William Westerlund
November 6, 2025
Read time
Picture two teams moving fast on different platforms. Engineering lives in Slack while sales and finance operate in Microsoft Teams. People copy links between tools and miss updates. This guide shows practical ways to connect Slack and Microsoft Teams so you can align meetings, send reliable notifications, or enable full two-way chat without forcing a migration.
4
Integration Levels
2
Admin Systems
3
Use Case Tracks
Why Connect Slack And Microsoft Teams
Most companies end up with both tools after growth, mergers, or team preference. Integration reduces silos, keeps conversations in one place per team, and avoids constant context switching.
🧩
Interoperate Instead Of Migrate
A full migration is costly and disruptive. Interoperability lets each group stay productive while bridging gaps for meetings, alerts, and cross team chat.
⚡
Automate The Boring Work
Use targeted notifications for status changes and approvals. If your team relies on workflow automation, connect triggers to the right channels on both sides.
📚
Keep Context With The Work
When projects run in Slack, keep plans and checklists visible. Learn simple approaches to project management in Slack and link decisions to the correct threads.
💡
Mindset: Pick the lightest level that solves your problem. Do not jump to full chat federation unless your teams need true two way conversations.
Integrating Files, Calendars, And Workflows
Communication is just one layer. To fully connect Slack and Teams, you can integrate their associated tools.
SharePoint And Slack
If your organization stores files in SharePoint (via Teams), add the Microsoft OneDrive app to Slack. This lets you share and preview SharePoint or OneDrive files directly in Slack without leaving the workspace.
Outlook Calendar
Slack offers a native Outlook Calendar App. Once connected, it syncs your Teams meeting invites automatically. You will receive Slack reminders for upcoming Teams calls and can join directly.
Tasks And Planner
Through automation tools, you can link Microsoft Planner or To Do with Slack reminders or task bots like Asana or Trello. That means when a task is created in one system, it updates the other.
Four Levels Of Slack And Microsoft Teams Integration
Move from quick wins for meetings to advanced, bidirectional chat. Each level has tradeoffs for cost, setup, and governance.
✅
Best For: Scheduling and joining Teams meetings from Slack without leaving conversations.
Microsoft Teams Calls App In Slack
This official app lets you start and join Microsoft Teams meetings directly in Slack. It does not sync chat, threads, or files.
1
Install At The Workspace Level
A Slack admin adds the Microsoft Teams Calls app from the Slack App Directory. For Enterprise Grid, install it for each workspace that needs it.
2
Connect Your Microsoft Account
Open the app in Slack and click Connect. Sign in with your Microsoft 365 account and allow requested permissions.
3
Start Or Join From Slack
Use /teams-calls in any channel or DM to post a join link. A Workspace Owner can set Teams as the default call provider for the phone icon.
⚠️
Limitations: Not a chat bridge. Not supported for Microsoft national cloud tenants like Government, Germany, or 21Vianet China.
✅
Best For: One way alerts from one platform into the other. Examples include build failures, ticket updates, or approvals.
Automation Platforms For Notifications
Use tools like Zapier or Microsoft Power Automate to trigger messages across platforms. This is reliable for alerts, not for conversations.
1
Choose A Trigger
Examples include a new message in a Slack channel, a new SharePoint item, or a status change. You can combine with helpful slash commands to standardize posting formats.
2
Post To The Target Channel
Create an action to send a message into a Microsoft Teams channel or back into Slack. Include links and short context so people can act quickly.
3
Avoid Chat Echo
Treat these as notifications only. Tell users not to reply in the mirror channel. If you need replies to sync, jump to Level 4.
💡
Tip: For structured processes, pair notifications with lightweight checklists or a shared to do list so owners and due dates remain clear in Slack.
✅
Best For: A single channel mirror built by a technical team that accepts one way posts and no identity mapping.
DIY Webhooks And Email Relays
Chain a Slack outgoing webhook to a Teams incoming webhook through a small service that reshapes payloads. This preserves visibility but not authorship, threads, or replies.
1
Create An Incoming Webhook In Teams
Save the unique URL. Messages that hit this URL show up in the target channel as a bot card.
2
Build A Small Transform Service
Receive Slack payloads, map fields, and post to the Teams webhook. Host it on serverless infrastructure for simplicity.
3
Enable Slack Outgoing Hook Or App
Point Slack to your service for the chosen channel. Test formatting and rate limits. Expect maintenance over time.
⚠️
Reality Check: All posts appear from a bot. Mentions do not resolve, threads do not sync, and replies stay split. Use this only when a simple mirror is acceptable.
✅
Best For: Organizations that must run real time cross platform chat with threads, edits, reactions, files, channels, and DMs.
True Interoperability Providers
Specialized vendors sync Slack and Teams conversations both ways. Users stay in their native app while messages, threads, reactions, and attachments translate in the background.
Bidirectional channel sync with thread preservation
Cross platform DMs and group DMs
Emoji reactions, edits, and deletes reflected on both sides
File and rich text handling with security controls
🛡️
Admin Reality: Requires Slack Workspace Owner approval and Microsoft 365 Global Admin tenant consent. Expect a security review and data flow assessment.
Level
Primary Use Case
Bidirectional Chat
Threads & DMs
Setup Complexity
Typical Cost
Level 1: Native Calls
Start and join Teams meetings from Slack
No
No
Low
Free
Level 2: Automation
One way alerts and status updates
No
No
Medium
Per task or flow
Level 3: Webhooks
DIY one way mirror of a channel
No
No
High
Dev time
Level 4: Interoperability
Two way chat across platforms
Yes
Yes
High
Per user
Governance And Security Checklist
Coordinate Slack and Microsoft 365 administration. Confirm permissions, app policies, and data handling before rollout.
🔐
Slack Workspace Owner
Review app approval settings. Pre approve required apps. Verify channel creation and guest rules. Document retention and export policies. Standardize commands and naming for mirrored channels.
🏛️
Microsoft 365 Global Admin
Allow third party apps and custom apps in Teams policies. Grant tenant consent in Entra ID for the vendor app. Confirm conditional access, DLP, and external access align with company policy.
🧪
Pilot And Audit
Run a limited proof of concept. Validate threads, reactions, and edits. Check license counts after the pilot. Record actual message paths and storage locations.
💸
Cost Watch: Interoperability vendors use per user pricing. Clarify whether licenses are required for all users or only for mapped users and whether any guest provisioning triggers extra Slack seats.
Choose The Right Integration Path
Match your goal to the simplest workable level. Add complexity only when it unlocks real collaboration value.
📞
Goal: Join Meetings From Slack
Use Level 1. Install Microsoft Teams Calls in Slack and standardize on /teams-calls to post join links.
🚨
Goal: Post Alerts Across Tools
Use Level 2. Build notifications with automation. Avoid replies in the mirror channel to prevent split discussion. Pair with checklists for handoffs.
💬
Goal: Run Cross Platform Chat
Use Level 4. Pilot an interoperability vendor. Confirm thread sync, DM support, and edits before expanding.
Troubleshooting Slack And Teams Integration
Common issues and quick fixes across all levels.
🔑
Cannot Install Or Connect
Check who can add apps in Slack. In Teams, allow third party apps and verify permission policies. Confirm you are not on a Microsoft national cloud that blocks the Calls app.
🧵
Replies Do Not Sync
This is expected for Levels 2 and 3. Use a Level 4 provider if you require bidirectional threads and DMs.
🧭
People Are Lost Between Tools
Publish channel naming rules and a one page guide. Keep plans visible in Slack with simple project views so decisions are easy to find.
Keep Work Flowing Where Conversations Happen
Use Slack for chat and Teams for meetings while Suptask turns messages into tickets and tracked work inside Slack. Capture requests, assign owners, and keep context without switching tools.
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Frequently Asked Questions About Slack And Teams
Does The Microsoft Teams Calls App Sync Chat
+
No. It only starts and joins Teams meetings from Slack. Use a Level 4 provider for chat sync across platforms.
Can I Mirror A Channel Without A Vendor
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You can chain webhooks for a basic one way mirror. Expect bot authored posts, no mentions, no threads, and ongoing maintenance. For two way chat, use interoperability.
How Do We Manage Costs For Interoperability
+
Confirm whether pricing is all user or mapped user only. Run a pilot and review license counts after provisioning. Use automation for alerts where chat sync is not required.
Where Should Project Work Live After Integration
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Keep the project source of truth in Slack if your team collaborates there. Use simple checklists and to do lists and link major decisions to threads so context stays with the work.
What Happens If We Reply To Automation Posts In Teams
+
Replies stay in Teams. The Slack side does not see them. This splits context. If replies must sync, plan a Level 4 rollout.
Connect Slack And Microsoft Teams With Confidence
Start with meetings, add targeted notifications, and adopt full chat interoperability only where it pays off. Keep plans, tasks, and decisions visible with smart Slack practices.
