Second row Lewis Stevenson has been released from his contract with Ulster by mutual agreement and he will join Exeter Chiefs with immediate effect.
Stevenson was under contract until the end of the season, but having started just four games during this campaign, an early release was agreed to allow him to explore other options.
The 31-year-old lock had a spell with Exeter during the 2008/09 season, before a two-year spell with Harlequins and then a move back to Belfast in 2011 to join Ulster.
Stevenson, educated at Ballyclare High School, made 89 appearances for his home Province, scoring one try, which came against Treviso at Kingspan Stadium earlier this season.
Commenting on his departure, Stevenson said: "I am extremely proud to have played a part in this Ulster team over the last five seasons.
"Every time I pulled on the shirt it meant something to me. However, the time is right for me to face a new challenge and I am excited about being part of Exeter Chiefs again.
"I appreciate how Ulster has handled this and I wish them every success for the rest of the season.”
Exeter boss Rob Baxter said: "Having played here before, Lewis knows the club and we know him. We're very aware of the qualities he can bring to the squad and what kind of character he is, so he ticks a lot of boxes for us.
"We're delighted to have him on board until the end of the season. We know he will come in and offer us a lot, but at the same time we've got guys like Geoff Parling, Ollie Atkins and Jonny Hill who are playing some fantastic rugby right now.
"Now he's here, we'll look to get him up to speed as quickly as we can and get him involved and ready for what we know is going to be a big period of games for the club.
"I have to thanks Ulster for their efforts and ensuring the deal has gone through,” said Baxter. "They could have been well within their rights to do nothing, but they haven't done that and they've worked very closely with us in getting everything tied up pretty quickly.”