The team also came to terms with the other seven members of its 2012 draft class, an unusual move given that a team's draft picks are usually signed over time in the weeks following the draft.
The terms of the deals announced Monday were not released.
Selecting Irvin so high was considered a reach by some. He had been considered a likely second-day pick. But he became the centerpiece of a draft focused on defense, with most of Seattle's selections landing on that side of the ball.
The 6-foot-3, 245-pound Irvin played two seasons at West Virginia, where he had 14 sacks as a junior, and 8 1/2 sacks in his final season.