The ban stems from his three offseason arrests, which predated his time with the Dolphins, a source told ESPN's Cameron Wolfe.
"The conduct of our players is very important and Mark has done everything we have asked of him both on and off the field since signing with the Dolphins," head coach Brian Flores said in a statement. "We look forward to having him back at the conclusion of his suspension."
Walton emerged as the Dolphins' primary running back after beginning the season below Kenyan Drake and Kalen Ballage on the depth chart. Miami traded Drake to the Arizona Cardinals before the Oct. 29 deadline, but reportedly knew a suspension was looming for Walton.
In seven games this season, Walton has rushed for 201 yards, averaging 3.8 yards per carry. He was a fourth-round pick of the Cincinnati Bengals in 2018.