How can Teams phone numbers be synced automatically to on-premises Active Directory?

A scheduled PowerShell job can handle this. Use the Teams or phone-system API to retrieve assigned numbers, match them to the corresponding users, and update the selected AD attributes. Running it on an internal Windows server as a scheduled task is straightforward, though an Azure Automation runbook is another option if it can securely reach your directory.

Choose one system of record before automating anything. If AD drives the address book, populate telephoneNumber—and mobile or ipPhone only when you have a clearly defined purpose—and allow the normal Entra synchronization to carry the data onward. Exclude call queues, auto attendants, unassigned numbers, users who should not be listed, and people with pending offboarding. A two-way sync can overwrite intentional exceptions or create a loop when someone changes a number manually.

We query our phone provider’s API, write the results into the standard telephoneNumber attribute in on-premises AD, and let Entra Connect synchronize the changes. The script runs on an internal server several times a day. This works well when the carrier or phone platform is the authoritative source rather than trying to maintain a two-way sync.