Seattle is sending a fifth-round pick back to D.C., reports ESPN's Adam Schefter.
Dunbar had requested a trade or release in February, and the Redskins reportedly made the corner available Sunday.
The 27-year-old was the NFL's second-highest-graded cornerback last season, according to PFF. He's entering the final season of a three-year, $10.5-million extension signed in 2018.
Dunbar now jumps from a 3-13 outfit to a Seahawks team that went 11-5 and reached the divisional round of the playoffs in 2019. He'll form a tandem with Shaquill Griffin in Seattle's secondary.