Matthews, 29, was out of work for four games after being released by the Tennessee Titans -- a move he requested. He was unhappy with his role in the offense and complained to management after catching only three passes for 11 yards in the first three games.
The Jets (3-4) needed a body because leading receiver Quincy Enunwa (high ankle sprain), who didn't play last week, is expected to miss a few more games. Terrelle Pryor suffered a groin injury and was released, although there's a chance he could return when healthy. That, of course, could depend on how Matthews fares.
To make room for Matthews, the Jets placed safety Doug Middleton (torn pectoral muscle) on injured reserve. It means they have only two healthy safeties on the roster, Jamal Adams and Terrence Brooks.
In Sunday's loss to the Minnesota Vikings, the Jets' receivers struggled to get open, finishing with only seven catches on 21 targets. Starter Jermaine Kearse had no catches and seldom-used backups Andre Roberts, Charone Peake and Deontay Burnett each had drops.
Jets linebacker Avery Williamson, who played with Matthews in Tennessee, called him "a phenomenal player. ... He's a passionate player and talented, very talented."
Speaking on WFAN radio in New York, Williamson added, "He can go. He can go. He can add some great things to the receiving corps. Great hands and he can make something out of nothing. I've seen him make some phenomenal catches."
Matthews will join Kearse and Robby Anderson as their most accomplished receivers.
On Monday, coach Todd Bowles expressed concern about the lack of depth, saying "the more we get nicked up, we've got to have numbers ... to produce. Certain guys are going to certain packages and have to get more reps, and have to come around faster than usual."
Matthews was the Titans' leading receiver in 2016 and 2017, with 118 catches for 1,740 yards and 13 touchdowns. In fact, he signed a one-year contract extension in late August, but he never clicked in the Titans' new offensive scheme.
He sparked controversy last season by protesting the national anthem, remaining in the tunnel for a handful of games while the anthem was played. The Jets have had no player protests since it became an issue.
Matthews began his career with the Miami Dolphins in 2012. In his career, he has 228 catches for 3,147 yards and 21 touchdowns.