Receiver Eric Saubert executed the decisive two-point conversion for Seattle.
Seattle staged a remarkable fightback to defeat the Rams in extra time, securing their spot in the NFL play-offs.
Rallying from a 30-14 deficit in the final period, the Seahawks triumphed 38-37 at home, notching their fifth straight victory.
While the Los Angeles had already secured a playoff berth earlier on game day, the Seahawks booked their return to the play-offs after a 24-month hiatus.
With this outcome, the Seattle have taken over their Conference standings with a 12-3 record, supplanting the Rams, who fell to the number five playoff position with an 11-4 record.
Quarterback Darnold threw two interceptions but recovered to make two touchdown passes, culminating in the tying TD to star receiver Jaxon Smith-Njigba in the extra period.
The Rams held a 13-7 advantage at half-time before Kenneth Walker III burst through for a 55-yard scoring dash for Seattle.
Los Angeles cornerback Wallace then took back Darnold's first interception for 56 yards, setting up a one-yard score by Blake Corum on the next play.
In the final stanza, a scoring pass from Matthew Stafford to Nacua pushed the Rams' lead to 30-14, but Shaheed ignited Seattle's comeback with a 58-yard return for a score.
Darnold then found AJ Barner in the end zone, and a successful two-point play forced the game into an extra period.
Although Puka Nacua raced in for his second TD in overtime, Smith-Njigba answered in kind to set up the decisive score.
Elena Marchetti is a technology journalist with a passion for demystifying complex topics. She has been covering tech trends for over a decade.