The Dallas defense forced nine Buffalo turnovers. (AP)
Troy Aikman passed for four touchdowns, Emmitt Smith rushed for 108 yards, and the Cowboys converted nine turnovers into 35 points while coasting to the victory.
Dallas's win was its third in its record sixth Super Bowl appearance; the Bills became the first team to drop three in succession.
Buffalo led 7-0 until the first two of its record number of turnovers helped the Cowboys take the lead for good late in the opening quarter.
First, Dallas safety James Washington intercepted Jim Kelly's pass and returned it 13 yards to the Bills' 47, setting up Aikman's 23-yard touchdown pass to tight end Jay Novacek with 1:36 remaining in the period. On the next play from scrimmage, Kelly was sacked by Charles Haley and fumbled at the Bills' 2-yard line where the Cowboys' Jimmie Jones picked up the loose ball and ran two yards for a touchdown.
Dallas, which recovered five fumbles and intercepted four passes, struck just as quickly late in the first half, when Aikman tossed 19- and 18-yard touchdown passes to Michael Irvin 18 seconds apart to give the Cowboys a 28-10 lead at intermission. The second score was set up when Bills running back Thurman Thomas lost a fumble at his 19-yard line.
Buffalo scored for the last time when backup quarterback Frank Reich, playing because Kelly was injured while attempting to pass midway through the second quarter, threw a 40-yard touchdown pass to Don Beebe on the final play of the third period to trim the deficit to 31-17.
But Dallas put the game out of reach by scoring three times in a span of 2:33 of the fourth quarter.
Aikman, the game's most valuable player, completed 22 of 30 passes for 273 yards.
The victory was the ninth in succession for the NFC over the AFC.