Starting in 2023, the first two years of the contract will see Koroisau remain at Concord until at least the end of the 2024 season, while 2025 has been posed as a mutual option for both club and player, with the Tigers confirming the nature of the contract in a statement on Friday.
The star hooker, who was part of New South Wales' State of Origin squad this year, before going on to win the second premiership of his career as the Panthers beat the Rabbitohs in the grand final, has been one of the most hotly-chased signatures on the market.
His name has been, at times, shielded by the intense speculation regarding fellow hookers Brandon Smith and Reed Mahoney, while teammate Viliame Kikau's leaked photo in a Bulldogs shirt has also taken plenty of the attention.
But the 145-game veteran Koroisau, widely regarded as one of the best hookers in the competition, is an excellent pick up for the Tigers, although it's unclear at this stage how it will impact both Jake Simpkin and Jacob Liddle, who are contracted at the Tigers into 2023.
“We’re very pleased to have secured Apisai from the start of the 2023 season,” Sheens said.
“He not only adds a further level of experience in a key position of the spine, but he has shown himself to be successful alongside Head Coach Michael Maguire previously in his career.
“It is always a big positive to sign a player with international and State of Origin experience, and what Apisai has achieved at both club and representative level will be a great addition to what we are building here.”
For the Panthers, it means Koroisau is set to join Kikau out the door in a blow for the men from the foot of the mountains, given their previous aspirations of hanging onto both players despite a bloated salary cap.
The Tigers are among the favourites to take out the 2022 wooden spoon, having finished in the bottom four this season, and will be desperate to turn things around both before, and after Koroisau's arrival in 2023.