The winning kick was the fourth field goal of the game for Suisham, who helped Pittsburgh (8-3) take its third win in four contests.
Ben Roethlisberger amassed 246 yards, going 20-of-33 through the air for the Steelers (8-3), who entered the game tied with Baltimore atop the AFC North.
Rashard Mendenhall piled up 151 yards and a touchdown on 36 carries and Hines Ward made seven catches for 107 yards in the Steelers' win.
The Bills (2-9) saw their two-game winning streak snapped with the loss.
Ryan Fitzpatrick gained 265 yards with one score and an interception while Fred Jackson collected 104 yards and a touchdown on five catches for Buffalo.