While it's not as big as the Darrelle Revis signing, Ridley's addition gives the Jets at least one running back with a 1,000-yard season on his rsum.
Ridley's one-year contract with the Jets was finalized Wednesday.
The 26-year-old Ridley issued a statement Wednesday night on Instagram, thanking the Patriots and their fans.
"Sending love to all my day one fans, and every teammate I've had the pleasure to take the field with," Ridley posted. "We all know it's a business, yet it's also a blessing. So either way you see it, you'll never understand. Love New England, Love my former teammates, and I'm truly thankful for the opportunity the Patriot's organization has blessed me with. However it's #ontotheJETS."
Contract details weren't immediately available.
"He's excited for the opportunity and his rehab is going strong at this point," Ridley's agent, Andy Simms, told The Associated Press.
The Jets were investigating second-tier running backs to replace Chris Johnson, whose option wasn't exercised in February.
Ridley is similar to Ivory in that he's a between-the-tackles runner, used primarily on first and second downs. But he doesn't offer much as a receiver with only 23 career receptions.
The Jets still don't have a game-breaking player in the backfield. The 5-foot-11, 220-pound Ridley has shown the ability to be a No. 1 running back, rushing for a career-high 1,263 yards on 290 carries in 2012. He had 12 touchdowns that year as well.
But the Patriots, unlike some other teams in the NFL, don't consistently employ a No. 1 running back as they sometimes lean more heavily on their change-of-pace running back if their game plan calls for more passing.
That may explain why Ridley's production dipped in 2013, when he rushed for 773 yards on 178 carries -- a 4.3 average.
Hitting the unrestricted free-agent market for the first time this year, it's a case of bad timing for Ridley, who tore his ACL in an Oct. 12 game against the Buffalo Bills and was placed on season-ending injured reserve.
Ridley became the 15th new player for the Jets, one of the busiest teams in the offseason.
ESPN.com Patriots reporter Mike Reiss and The Associated Press contributed to this report.