The Steelers rallied from a 10-point third-quarter deficit to score the game's final 13 points, including Pickett's go-ahead touchdown pass for the dominant Najee Harris with 56 seconds left.
Minkah Fitzpatrick intercepted Ravens quarterback Tyler Huntley's desperate pass with 13 seconds remaining to clinch victory for the Steelers, who claimed their third straight win to improve to 8-8 behind the Cincinnati Bengals (11-4) and Ravens (10-6) in the AFC North.
The Ravens' defeat, which is the fourth time they have lost after having a double-digit lead this season, significantly impacts their aspirations to win the division, with the Bengals able to clinch it with victory against the Buffalo Bills on Monday. The Bengals host the Ravens in Week 18.
Pickett and Harris were the stars for the Steelers, with the 24-year-old quarterback completing 15 of 27 passes for 168 yards with his only touchdown coming when it mattered most.
In the game-winning 11-play drive, the QB made 20-yard and 28-yard gains with passes to Pat Freiermuth and Steven Sims Jr respectively before evading Jason Pierre-Paul's tackle and finding Harris in the left corner on a third-and-8.
Steelers running backs Harris (111 rushing yards on 22 carries) and Jaylen Warren (76 rushing yards on 12 carries) were outstanding. Huntley completed 14 of 21 passes for 130 yards for the Ravens.
Earlier, the Ravens benefitted from a controversial unnecessary roughness penalty against Cameron Heyward on a third-and-14, which led to a verbal exchange with team-mate Fitzpatrick, after Huntley threw a touchdown pass for Isaiah Likely on the next play shortly prior to half-time.