Zac Laybutt has represented Papua New Guinea in eight Tests and will join the PNG Chiefs in 2028.
He debuted for the Kumuls in 2023, helping them win the Pacific Bowl championship against Fiji.
Laybutt also appeared at the 2026 Rugby League World Cup.
The Chiefs have signed him on a two-year deal, which begins after he completes his Cowboys contract in 2027.
He has played 42 NRL games since his 2023 debut and can cover wing and centre, as well as kick goals for club and country.
He will be the club's Player #008 and its fifth Kumuls representative signing.
Alex Johnston was announced as Player #002, while Finley Glare, Gairo Voro and Morea Morea have development contracts for 2028.
Chiefs CEO Lorna McPherson said: "We are delighted to have signed Zac, and his signing is particularly meaningful for us as we build a club that proudly represents PNG,"
Coach Willie Peters said Laybutt would bring NRL experience and a willingness to work hard for the team.