However, he progressed quickly thanks to his advantageous physique and represented Connacht on several occasions in the youth categories, notably in the under-18s.

During the 2017-2018 season, he participated in four British and Irish Cup matches with the Connacht Eagles, the province's reserve team.

Four years after starting rugby, Niall Murray made his professional debut with Connacht on 14 December 2019, on the fourth day of the European Cup of the 2019-2020 season, against Gloucester.

[citation needed] For his first professional season, he participated in seven matches, including three as a starter, before the premature end of competitions linked to the Covid-19 pandemic.

[citation needed] At the start of the 2020-2021 season, he suffered a shoulder injury forcing him to undergo surgery.

That season, his province qualified for the quarter-finals of the United Rugby Championship where his team eliminated Ulster, before being beaten in semi-final by the Stormers.