ESPN's Josina Anderson was the first to report it being a one-year deal.
"I'm definitely excited about the opportunity to play in Seattle," Winfield told Anderson. "They're a great football team. Those guys did an excellent job last season. They're young, athletic and energetic. I'm excited to play with Richard (Sherman), Brandon (Browner), Kam (Chancellor) and Earl (Thomas) because they're some of the most talented players on defense in the NFL right now."