The Playboy Club star will appear in the TNT cop drama's third season, according to TVLine.
Cibrian - the husband of singer LeAnn Rimes - will play Dennis Rockmond, a motivational speaker who shares a spark with Isles (Sasha Alexander).
The actor appeared on soap opera Sunset Beach from 1997 to 1999 and has since starred on CSI: Miami, Ugly Betty and Third Watch.
His last show The Playboy Club was axed by NBC after just three episodes. Cibrian was also injured on set hours after the cancellation, while his California home was damaged in the same week when a suspected drunk driver crashed into his fence.
Rizzoli & Isles was picked up for a third season in August, after the second season premiere drew 8.6m viewers.
A new run of 15 episodes begins on June 5 on TNT. In the UK, the series airs on digital channel Alibi.
> Rizzoli & Isles star Lee Thompson Young for CSI: NY role
Watch a promo for Rizzoli & Isles below: