A 200 cm tall ruckman, Byrne started his career at Melbourne in 1977 and one game into his sixth season with the club decided to cross to Hawthorn.

In 1983, Byrne finished equal fifth in the Brownlow Medal and was a member of Hawthorn's premiership side, kicking three goals in the Grand Final.

In 1998 he became head coach of University side Bulldogs in New South Wales where he remained until 2001 before a change of codes saw Byre become more active in rugby union.

In 2001, he left Australia with he took up various consultancy stints; firstly South Africa in 2001, before heading to Europe in 2002 to take on a skills based role with the Scottish national team between 2002 and 2005.

[7] When Byrne left New Zealand in December 2015,[6] the team had accrued a win percentage above eighty-seven percent and is often praised as having deep involvement in building the "All Blacks Empire".

On 24 September 2021, Byrne was announced as the head coach of the Fijian Drua ahead there first season in the Super Rugby (2022).

In his first season in charge, the Drua only managed to win two games, coming against fellow Pacific team Moana Pasifika and Australian side Melbourne Rebels.