Receiver Eric Saubert executed the decisive two-point conversion for Seattle.
Seattle staged a stunning comeback to defeat the Rams in extra time, clinching their spot in the postseason.
Overcoming a 30-14 deficit in the fourth quarter, the Seattle squad triumphed by a single point at home, notching their fifth consecutive win.
While the Los Angeles had already secured a post-season berth earlier on game day, the Seattle team booked their return to the postseason after a two-year absence.
With this result, the Seattle now lead their division's standings with a twelve and three record, supplanting the Los Angeles, who dropped to the number five seed with an eleven and four record.
Quarterback Sam Darnold had two picks but regrouped to make two touchdown passes, culminating in the tying TD to star receiver Smith-Njigba in overtime.
The visitors held a six-point advantage at half-time before Kenneth Walker III broke free for a 55-yard touchdown run for Seattle.
Los Angeles defensive back Wallace then took back Darnold's first pick for 56 yards, setting up a short score by Blake Corum on the ensuing snap.
In the final stanza, a scoring pass from Stafford to Puka Nacua extended the advantage to sixteen points, but Rashid Shaheed ignited the comeback with a 58-yard return for a score.
Darnold then connected with AJ Barner in the endzone, and a successful conversion sent the contest into an extra period.
Although Nacua raced in for his second TD in overtime, Smith-Njigba responded in kind to set up the game-winning conversion.