Reagan Campbell-Gillard will join Parramatta on a five-year deal starting in 2020 after Penrith formally granted the prop a release.
The former Australian forward was contracted to the Panthers until 2024 but the club agreed to cut ties with the 26-year-old to free up salary cap space.
The Eels confirmed Campbell-Gillard's signing on Saturday. The big man will add starch to the club's forward ranks with Tepai Moeroa, Tim Mannah and Manu Ma'u to depart after this season.
"We're continuing to build our roster and the addition of Reagan, a representative forward, is a great fit for our team," Parramatta general manager of football Mark O'Neill said.
Campbell-Gillard took to Instagram after it became official that he had joined Parramatta, saying "things happen for a reason".
He also said "sometimes good things fall apart so better things can fall together" and acknowledged Penrith fans, club officials and his former coaches.
Penrith general manager of rugby league Matt Cameron said a mutual decision on Campbell-Gillard's future was reached after "lengthy discussions" with the front-rower and his management.
“The decision to grant this release was not taken lightly. Management of the club’s salary cap is a detailed and complex exercise that at times requires difficult decisions to be made to ensure sustainability," Cameron said.
“While it is always disappointing to see local juniors leave Panthers, this outcome provides our club with crucial salary cap flexibility not only next year but also in future years.
“As a club we thank Reagan for his service and wish him the best of luck moving forward.”
Campbell-Gillard played 114 matches for Penrith after debuting in 2015. He struggled for form throughout 2019 and was briefly sent to the Canterbury Cup.