Massaquoi, the 50th overall selection in the NFL draft, agreed to terms on Tuesday, the Browns announced.
Terms of the deal were not disclosed.
Massaquoi ranked fourth on the school list at Georgia, where he recorded 158 catches for 2,282 yards and 16 touchdowns. He also was a first-team All-Southeastern Conference and Academic All-SEC member in 2008.
The Browns signed their first-round pick, center Alex Mack, last weekend.
Cleveland has only one unsigned draft choice, Brian Robiskie, an Ohio State receiver taken in the second round.