Mendenhall, who has played in only four games this season because of injuries, will miss the Steelers' game against Dallas Sunday.
Details of his offending behavior were not provided.
The 25-year-old running back has 113 rushing yards on 34 carries.
Running back Baron Batch was promoted to the active roster from the practice squad to fill Mendenhall's roster spot.
Swim Week Miami Beach 2014 [PHOTOS]