The 28-year-old Lockett was entering the final season of a three-year, $31.8 million extension that he signed in 2018. Since then, he has had his three best seasons, recording 28 receiving touchdowns and 3,076 yards.
The Seahawks selected Lockett in the third round of the 2015 draft out of Kansas State. He was named to the Pro Bowl in his rookie season after hauling in 51 passes for 664 yards and six touchdowns.
Last season, Lockett and fellow wideout D.K. Metcalf became only the second pair of Seahawks receivers in franchise history to both surpass 1,000 receiving yards in the same year.
Lockett has crossed the 1,000-yard mark in each of the past two seasons. In 95 career games, he has notched 376 receptions for 4,892 yards and 37 touchdowns.