Raiders senior executive John Herrera said the trade will be official once the league approves it and Curry passes his physical.
Curry failed to live up to the high expectations of being a high draft pick and lost his starting job earlier this year. The Seahawks decided to cut ties after 2½ seasons, acquiring a 2012 seventh-round pick and a conditional fifth-rounder in 2013 for a player once considered a "can't miss" star.
The pick can be raised to a fourth-round pick based on Curry's playing time with Oakland, a source told ESPN senior NFL analyst Chris Mortensen.
This move is the first the Raiders have made since the death of longtime owner Al Davis, who also served as general manager and ran the football operations.
This is just the type of deal that Davis probably would have liked. The Raiders have often had success acquiring former high draft picks who were struggling. Curry would be the 12th former first-round pick on the Raiders roster, including seven on defense.
Curry was absent from Seahawks practice on Wednesday and his locker was cleaned out. Some of his former Seattle teammates confirmed Curry had come to the team's facility earlier in the day to say his goodbyes.
"He came in and said how much he had learned from us and how much he's going to miss us and everything. It's a new beginning for him and hopefully he steps to the plate," linebacker Leroy Hill said. "I think down there he won't have all those high expectations that he had here so he can relax and just play ball. I wish him luck and think everything will work out for him."
Curry had fallen out of favor in Seattle, with rookie K.J. Wright taking over the starting strongside linebacker role. It was a rapid fall for a player taken No. 4 overall in 2009.
The Butkus Award winner his senior year at Wake Forest, he was never able to make the complete transition to the pro game. Whether he was playing on the line of scrimmage, as a rush defensive end, even a third-down specialist, or this season playing back from the line, he struggled to find a place where he could be successful.
He struggled especially in pass coverage, to the point where he was replaced by recent free agent signing David Vobora at times in the fourth quarter of last week's 35-26 win over the New York Giants. Vobora had just been re-signed by the Seahawks earlier that week.
Curry allowed eight receptions on eight attempts in his direction for 120 yards, according to STATS LLC. For his career, Curry has allowed 62 catches in 76 attempts for 613 yards and six touchdowns for a 126.6 passer rating.
The Raiders are banged-up at linebacker with starting middle linebacker Rolando McClain slowed by an ankle injury and backup Ricky Brown placed on injured reserve last week. Starting strongside linebacker Kamerion Wimbley also could be seeing more time as a rush defensive end with starting end Matt Shaughnessy out with a shoulder injury.
Coach Hue Jackson talked to the media before reports of the deal surfaced and was not available to comment on it until Thursday.
Curry was first benched in favor of Wright in Week 3. He first expressed frustration at the benching, but then said a few days later that he was at peace with the decision to go with Wright. He was asked on Sept. 29 if he felt like he needed a fresh start after his struggles in Seattle.
"Who knows. I don't know if I can sit here and say if that is the truth or if it is not," Curry said. "I've never been in that situation. I don't know personally many of the guys who've been through the situation of having a fresh start. So I really don't know."
Curry's future in Seattle was already tenuous after his contract was restructured, with Curry giving up a large chunk of guaranteed money that was expected to come his way in 2012 and freeing the Seahawks to part ways with Curry after this season.
"He gets to go to a new team, show the team who he is and just show them what kind of person he is," Wright said. "He told us that before he left. So he's just starting over. I think it's going to work out good for him."
Information from The Associated Press contributed to this report.