The contract is worth $87.6m with $60m in guaranteed money, according to both Sports Illustrated and ESPN.
That puts Wilson on par with Green Bay Packers quarterback Aaron Rodgers, who is the NFL's highest-paid player with a deal worth an average of $22m annually.
Wilson, who was a third-round pick in the 2012 draft, was scheduled to earn $1.54m in 2015 during the final year of his rookie contract.
The 26-year-old tweeted his delight at the deal on Friday: "Blessed to be w/ this organization for 4 more years! Can't wait to get on field w/ the fellas! @Seahawks #ChampionshipMindset."
Wilson has been a sensation for the Seahawks since beating out high-priced free agent Matt Flynn in training camp of his rookie year and has arguably been the league’s best bargain over the past three seasons.
Seattle, led by Wilson, has reached back-to-back Super Bowls over the past two seasons, defeating the Denver Broncos in 2013 before losing to the New England Patriots a year later.
The former Wisconsin Badger has earned a reputation as one of the most "clutch" players in the NFL and has orchestrated 15 fourth-quarter comebacks since 2012, the best in the league during that span.
Through his three NFL seasons Wilson ranks first in total wins (42), playoff wins (6) and Super Bowl starts (2). He's also second in passer rating (98.5) and fourth in touchdown passes (84).