Financial terms were not released, but a source told ESPN.com's Terry Blount the deal is for three years at $13 million with $9 million guaranteed.
Baldwin was scheduled to make $2.2 million this season as a restricted free agent. The new deal allows Baldwin to hit unrestricted free agency after the 2016 season, when he'll be entering his seventh year in the league.
The contract is in line with the Seahawks' philosophy of signing productive young players to relatively short-term deals. Their thinking: A shorter contract rewards a player financially while also serving as an incentive for a shot at another lucrative extension when the deal expires.
In April, safety Earl Thomas, coming off his third Pro Bowl appearance in his first four seasons, signed a four-year, $40 million extension that included $27.75 million in guarantees. Nearly two weeks later, cornerback Richard Sherman, who had a league-high 20 interceptions in his first three seasons, signed a four-year, $56 million extension that reportedly includes $40 million in guarantees.
Baldwin has consistently produced since joining the Seahawks as an undrafted rookie in 2011. He led the team's receivers in catches (51), yards (788) and touchdowns (four) that season, and last season ranked second in receptions (50) and yards (778) and tied for first with five touchdowns.
He was particularly effective in the playoffs, his 24-yard catch on third-and-3 early in the fourth quarter of the divisional round helping stall a Saints rally and set up the decisive touchdown, and his 51-yard reception in the NFC Championship Game win over the 49ers setting up the Seahawks' first points after they trailed 10-0. He finished that game with six catches for 106 yards.
Neither Baldwin nor the Seahawks were immediately available for comment.
ESPN.com Seahawks reporter Terry Blount contributed to this report.