Macdonald was with the St George Illawarra Dragons this season after debuting for Sydney Roosters in 2014.
According to the North Queensland Cowboys official website, Macdonald has arrived at the club’s camp in preparation for the 2019 season.
The 24-year-old recently participated in the PM’s XIII in Port Moresby where Australia beat PNG 34 – 18.
Born in Port Moresby but growing up in North Queensland, Macdonald debuted in the red, black and gold jersey in 2013 – when he was 19 years of age.
So far he has played nine Test matches for the PNG Kumuls.