The team didn't disclose terms of the contract.
Massaquoi, 26, started five games last season for the Cleveland Browns, finishing with 17 catches for 245 yards. Injuries limited him to nine games overall in 2012.
The 6-foot-2, 227-pound receiver made 118 catches for 1,736 yards and seven touchdowns with Cleveland after being selected in the second round (No. 50 overall) of the 2009 draft.
In Jacksonville he'll join a wide receiver corps that includes likely starters Justin Blackmon and Cecil Shorts plus Jordan Shipley, who signed this offseason and is a candidate to fill the slot receiver role.