During the season, Isaako's form for the Magpies prompted Broncos coach Wayne Bennett to debut him in NRL round 19 against the Newcastle Knights, starting at fullback in the 34–22 win at Hunter Stadium.[9] In round 1 of the 2018 NRL season against the St George Illawarra Dragons, Isaako starred as a winger for the Broncos in their 34–12 loss at Jubilee Stadium.[13] On 24 June 2018, Isaako made his international debut for New Zealand against England in the historical test match set in Denver, USA, starting on the wing and kicking three goals in the 36–18 loss at Mile High Stadium.[23][24][25] Isaako returned to his wing spot the following week against the 2018 premiers, the Sydney Roosters, and kicked three goals in the much needed 15–10 win at Suncorp Stadium.Due to his father's death in New Zealand and COVID-19 quarantine restrictions, he was unable to return to Australia and play for the second half of the season.[29] In round 10, Isaako scored the winning try for Gold Coast in their golden point victory over St. George Illawarra which ended a five-game losing streak.Even though the Dolphins did not qualify for the finals, Isaako recorded both the highest number of NRL tries and points in the 2023 competition; a feat last achieved by Canberra Raiders goal-kicking centre Mal Meninga in 1990.He scored two tries and kicked four goals as the new club pulled off a major upset defeating the Sydney Roosters 28–18 at Suncorp Stadium.[36] In round 5, he scored one try and kicked two goals in the Dolphins 12–38 loss to St George Illawarra Dragons at WIN Stadium.[43] Round 13 was Isaako's one-hundredth NRL game; he scored two tries and kicked five goals for the Dolphins in their 26–12 victory over the St. George Illawarra Dragons at Kayo Stadium.