When you join a Microsoft Teams chat, what happens depends on what kind of chat it is. In a normal one-to-one or group chat, you may be asked to accept the invitation before you can read or reply, and the other person may then be able to see your name and status.

What usually happens

  • For a new direct chat, you often get a chat request first, and the chat stays there until you accept or block it.
  • If you accept, you can see the messages and start chatting, and the other person may gain limited profile/presence access.
  • If you block, they can’t message you or see your status.
  • In a group chat, you may be able to preview messages before joining, and then decide whether to join or delete the chat.

Chat history

If someone is added to an existing group chat, they may or may not see earlier messages depending on how they were added and whether chat history was shared. In some cases, especially when people are added during a call, they only see messages sent after they joined.

Simple example

If a coworker adds you to a project chat, you might first see it as a request. After you accept, you can read the thread, send replies, and see future updates in that chat.

Useful note

If you meant joining a Teams meeting chat instead of a normal chat, the rules are a bit different: meeting chat can be available before, during, and after the meeting, and access can depend on whether you were invited, joined, or were added during the meeting.

TL;DR: joining a Teams chat usually means you either accept a request or are added in, then you can read and reply; in some cases, people can see your basic presence info, and chat history may be limited.