According to Sports Illustrated's Jim Trotter, Seymour and the Raiders agreed to a two-year deal with $22.5 million in guaranteed money.
It was reported earlier this month that Seymour would again have the franchise tag placed on him, but the team avoided that route this year.
If he earns the full $30 million, Seymour, 31, will become the highest-paid defensive player in the NFL with the new deal.
In 13 games last season, Seymour finished with 5.5 sacks and 48 tackles, as the Raiders finished with an 8-8 record.