Miami closed out a 3-1 pre-season while the Cowboys went 2-2. Neither starting quarterback, Chad Henne for Miami nor Tony Romo for Dallas, saw action.
Larry Johnson scored on a 22-yard run in the opening period, finishing off a 79-yard drive for the Dolphins.
Third-string Dallas quarterback Stephen McGee was 21-of-25 for 223 yards with an interception. Rookie DeMarco Murray gained 32 yards on the ground and caught 64 yards worth of passes for the Cowboys.
The teams will meet in Texas on Thanksgiving Day.
Miami opens its regular season at home with a Monday night game against New England. Dallas visits the New York Jets.