The NFL has been holding an independent investigation into allegations of sexual misconduct by 24 massage therapists.
All but one of those civil lawsuits were settled privately, but many expected a huge punishment for the quarterback of at least a season long suspension.
Former federal Sue L. Robinson issued the ruling on Monday, and the players' union have already agreed to stand by the decision, although they, Watson and the NFL have three days to appeal.
If his suspension is upheld, Watson will still be able to participate in practice during the pre-season. He will not be with the team during the first half of the suspension, but can return for the second half of the suspension.
Watson has maintained he is innocent throughout the process. Two grand juries in Texas declined to pursue criminal charges against Watson earlier this year.
"I met with the NFL a couple weeks ago, and I did everything they asked me to do, I answered every question truthfully that the NFL asked me," Watson told reports on June 14.
"I spent hours with the people they brought down, and that's all I can do is just be honest and tell them exactly what happened.
"I know they have a job and so I have to respect that, and that's what we wanted to do is cooperate. They have to make a decision that's for the league."
Jacoby Brissett is expected to be the starting quarterback for the Browns while Watson sits out the suspension.