If you've organized a Teams meeting, you can save a record of who's attended it. Here's how:
During the meeting, select Show participants and choose Download attendee list .
The report will download as a .CSV file that can be opened in Excel. The .CSV file contains the name, join time, and leave time of all meeting attendees.
Keep in mind that you'll only be able to download the attendance report while the meeting is in progress and participants are still present.
Only meeting organizers can download attendance reports. This option isn't available to other attendees.
This feature must be turned on by your admin. See Manage meeting policies in Teams for more info.