The contract will mean he is with the Redcliffe-based club until at least the end of 2025, and marks the second backline signing with NRL experience for the Dolphins after the earlier acquisition of Jamayne Isaako.
Jennings has struggled to gain playing time during his stint at Penrith, despite being able to line up on the wing or in the centres.
Added to some time out for injury during the middle of the season, Jennings has managed just three games since joining the Panthers at the start of 2021.
A Penrith junior, he made his NRL debut for Penrith in 2015, before moving to South Sydney in 2017, where he played 34 games over two years, before making another 26 appearances over three years to the end of 2020 at the Wests Tigers.
Brother of Michael and George, Robert has spent three games as the 18th man already this season, but is yet to make it onto the field for Penrith, having scored 33 tries in his 65 NRL appearances.
Instead, he has made nine NSW Cup appearances, scoring six tries and running for a tick over 100 metres per game in a dominant Panthers team who have only lost one of their first nine games.
A former Junior Kangaroo, junior Blue and Tongan representative, Dolphins' CEO Terry Reader said it was a big signing for the club.
“Robert has played at successful clubs and also has representative experience, so is a great acquisition for the Dolphins,” said Reader.
“He scored 19 tries in one season with the Rabbitohs and has averaged better than a try every two games across his NRL career.
“Those kind of statistics underline the fact that he has the power and ability to cause plenty of damage in the NRL for the Dolphins.”