Prop Sean McCarthy has re-signed for Jersey from Irish province Leinster.
The 24-year-old was an ever-present in the Championship for the Channel Islanders until he left last summer.
Jersey have also added Bath winger Rich Lane and Italian prop Cosma Garfagnoli to their squad for next season.
"I'm very excited to be rejoining the club after their most successful season in the Championship and look forward to contributing to an even better one next year," McCarthy told the club website.
"My year in Ireland has been very different to what I've been used to. There's huge competition for every position in the Leinster squad and game-time has been hard to earn."
Lane, 21, has played for Bath in the LV= Cup and European Challenge Cup, and has also spent time on loan with Cornish Pirates.
Former Benetton Treviso man Garfagnoli has experience at the top level in Italy, also playing for Lazio and most recently Petrarca.
"Rich has great potential and I'm expecting him to use his speed and power to good effect in our back-line," said Jersey head coach Harvey Biljon.
"Cosma has a reputation as a strong scrummager, who will also bring all-round rugby skills to our squad."
Jersey's new signings will join their team-mates for pre-season training next month and takes Biljon's squad up to 32 players.