Tight end Eric Saubert executed the decisive two-point conversion for Seattle.
Seattle staged a remarkable comeback to defeat the Rams in extra time, securing their spot in the postseason.
Rallying from a sixteen-point hole in the fourth quarter, the Seahawks triumphed by a single point at home, notching their fifth straight win.
While the Los Angeles had become the first to earn a playoff berth earlier on game day, the Seahawks booked their return to the play-offs after a two-year hiatus.
With this result, the Seattle now lead their division's standings with a 12-3 mark, supplanting the Rams, who fell to the number five seed with an 11-4 standing.
Quarterback Sam Darnold had two interceptions but recovered to deliver two touchdown passes, including the second score to wideout Smith-Njigba in the extra period.
The Rams held a six-point lead at half-time before Kenneth Walker III burst through for a 55-yard touchdown run for the home side.
Rams cornerback Josh Wallace then took back Darnold's initial pick for 56 yards, setting up a one-yard touchdown by Blake Corum on the next play.
In the final stanza, a touchdown from Matthew Stafford to Puka Nacua extended the Rams' lead to sixteen points, but Shaheed provided the hope with a 58-yard return for a score.
Darnold then found Barner in the endzone, and a successful conversion forced the game into overtime.
Although Puka Nacua scored for his second TD in OT, Jaxon Smith-Njigba responded in kind to set up the decisive score.