Moncrief will theoretically replace Allen Robinson, who reportedly signed with the Chicago Bears, but he joins a crowded wide receiver group in Jacksonville that now includes Marqise Lee, Allen Hurns, Dede Westbrook, and Keelan Cole.
Jacksonville will also reportedly sign guard Andrew Norwell - regarded as the top free agent offensive lineman - and is also re-signing wide receiver Marqise Lee, according to reports.
Moncrief, a third-round pick of the Colts in 2014, appeared in 53 games with 27 starts over his past four seasons.
Moncrief signs his deal the same day Danny Amendola goes to the Dolphins, Sammy Watkins agrees with the Chiefs and Paul Richardson signs with the Redskins.
Robinson intends to sign with the Chicago Bears, he told ESPN's Josina Anderson. He lost his starting job as the No. 2 receiver to Kamar Aiken at one point, and he finished with only 26 receptions for 391 yards and 2 touchdowns last season.
The Jaguars suffered a rash of injuries at receiver previous year that held them to bottom-16 numbers in both receiving yards and touchdowns. The Jaguars were expected to be active in the free-agent wide receiver market given the amount of interest Robinson had been generating when the Jaguars opted not to give him the franchise tag.