Moss caught a touchdown pass and then pretended to pull down his pants in front of Green Bay fans.
The fine was issued by Peter Hadhazy, the league's director of game operations.
"Your actions were based on poor judgment, did not reflect well on you or the Vikings, and were insulting to many," Hadhazy said in a letter to Moss.
"They have resulted in widespread criticism and needlessly detracted from Minnesota's dramatic playoff victory. Fans should look to you and your teammates to see how to compete and win in football. But when you lose your focus on playing and engage in sideshows as you did on Sunday, you forfeit much of this."