Tight end Eric Saubert made the game-winning two-point play for Seattle.
Seattle staged a remarkable fightback to defeat the Rams in overtime, clinching their place in the postseason.
Rallying from a 30-14 deficit in the fourth quarter, the Seahawks triumphed by a single point at home, notching their fifth consecutive win.
While the Los Angeles had already secured a playoff berth earlier on Sunday, the Seahawks secured their place to the play-offs after a 24-month absence.
With this outcome, the Seattle have taken over their division's race with a twelve and three mark, supplanting the Los Angeles, who dropped to the fifth playoff position with an 11-4 record.
Quarterback Sam Darnold had two picks but regrouped to make two scoring throws, including the second score to wideout Smith-Njigba in overtime.
The Rams held a 13-7 lead at half-time before Kenneth Walker III burst through for a 55-yard touchdown run for Seattle.
Los Angeles cornerback Wallace then took back Darnold's initial interception for 56 yards, setting up a one-yard score by Corum on the ensuing snap.
In the final stanza, a touchdown from Stafford to Puka Nacua extended the advantage to 30-14, but Shaheed provided Seattle's hope with a 58-yard punt return.
Darnold then found AJ Barner in the endzone, and a successful conversion forced the contest into an extra period.
Although Nacua raced in for his another TD in overtime, Jaxon Smith-Njigba responded in kind to set up the decisive score.
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Allen Warren
Allen Warren
Allen Warren