Garrett will not play again this season following his altercation with Mason Rudolph, having stripped him of his helmet before swinging it at the Pittsburgh Steelers quarterback during the closing stages of Cleveland's 21-7 win on Thursday.
The first overall pick of the 2017 draft has now been banned for the remainder of the season; he must "meet with the commissioner's office" before a decision is made over when exactly he can return to action.
Garrett, who was also fined, released a statement following the announcement of the punishment, again apologising to Rudolph, his team and the league.
"Last night, I made a terrible mistake. I lost my cool and what I did was selfish and unacceptable," the statement read.
"I know that we are all responsible for our actions and I can only prove my true character through my actions moving forward. I want to apologise to Mason Rudolph, my team-mates, our entire organisation, our fans and to the NFL.
"I know have to be accountable for what happened, learn from my mistake, and I fully intend to do so."
Browns head coach Freddie Kitchens said, according to the team's official Twitter account, they had to accept the punishment handed to Garrett, who has the option to appeal within three working days.
"You put it in their hands when you do something like that," Kitchens told the media on Friday.
Cleveland's Larry Ogunjobi received a one-game ban for unnecessary roughness, while Pittsburgh center Maurkice Pouncey was suspended for three games for aiming kicks and punches at Garrett in the immediate aftermath.
The Browns and the Steelers - who were both fined $250,000 by the league - meet again in Week 13 of the regular season.