The Jets released Decker on June 12 after unsuccessfully attempting to trade the veteran wide receiver.
Decker, 30, underwent hip and shoulder surgeries last fall, but he is healthy and had been practicing before the Jets released him.
Decker, who lives near Nashville with his wife, country singer Jessie James, visited the Titans last week after he was released.
Both Decker and his wife reacted to his homecoming on Twitter.
We are home 😍— Jessie James Decker (@JessieJDecker) June 18, 2017
Decker was limited to three games last season but caught 80 passes for 1,027 yards and 12 touchdowns in 2015. He also had two seasons of more than 1,000 yards receiving and double-digit touchdown totals for the Denver Broncos, who selected him in the third round (87th overall) of the 2010 draft.
In seven NFL seasons, he has 385 receptions for 5,253 yards and 52 touchdowns.
To create a roster spot for Decker, the Titans waived wide receiver Bra'Lon Cherry.
ESPN's Rich Cimini contributed to this report.