Isaac Redman had the go-ahead, seven-yard TD 9 win over the Cleveland Browns.
However, the Steelers (12-4) were unable to clinch the AFC North Division and the conference's No. 2 seed due to Baltimore's 24-16 win over Cincinnati on Sunday.
Pittsburgh, instead, will be relegated to the fifth seed in the AFC and a trip to Denver in the wild-card round.
After being held out of last Saturday's 27-0 rout of St. Louis, Ben Roethlisberger played the full 60 minutes on Sunday despite a high ankle sprain he suffered during Pittsburgh's 14-3 win over Cleveland on December 8.
Roethlisberger completed 23-of-40 passes for 221 yards.
Redman came on to replace Rashard Mendenhall after he injured his right knee on the final play of the first quarter. Redman finished with 92 yards on 19 carries, but fumbled twice in the fourth quarter. Mendenhall racked up 38 yards on the ground before exiting.
Colt McCoy missed his third consecutive game due to a concussion suffered against the Steelers. Seneca Wallace got the start and completed just 16-of-41 passes for 177 yards and an interception for Cleveland (4-12), which lost its final six games to close the season.