Dean announced his decision to leave Auburn on Instagram Friday night, hours after the Tigers' 63-14 win over Purdue in the Music City Bowl.
Dean had 30 tackles, two interceptions and nine pass breakups as a junior.
He's the second Auburn player to declare for the draft, joining quarterback Jarrett Stidham.
Dean played in 26 games the past two seasons. He initially signed with Ohio State before transferring.
He redshirted in 2015 and missed the following season with an injury.
Dean said Auburn gave him a chance to play after "football was almost taken away from me before I could even play a snap of college football."