New Zealand forward Awen Guttenbeil has decided to go ahead with his move to Castleford, despite their recent relegation from the Super League.
Guttenbeil is thought to have agreed to join Widnes had they been promoted
The 30-year-old second rower's switch looked to have collapsed when the Tigers lost their battle for survival.
However, the club have confirmed he will honour his two-year contract.
Guttenbeil will combine a playing role with coaching and he said: "I have a couple of years in me but this gives me a chance to dip my toe into coaching."
The Kiwi, who is currently with the New Zealand squad competing in the Tri Nations series, added: "I wanted to play Super League or in the Australia NRL, but there's a chance to get this team back to the Super League.
We are delighted that an established Test player has agreed to join the club
Castleford spokesman David Smart
"I was holding out to go to England."
Guttenbeil had 11 seasons at the New Zealand Warriors and his appearance total of 170 is second only to that of Stacey Jones.
Castleford spokesman David Smart said: "The deal was completed over the weekend and the paperwork was faxed over on Monday morning.
"We are delighted that an established Test player has agreed to join the club."
Guttenbeil will be assisting head coach Terry Matterson, who has also decided to stay with the club.