Hamill played for the Australian Institute of Sport in the 2009–10 A-League National Youth League where they failed to win a single game.

[2] On 23 April 2010 Hamill rejected numerous offers from English Premier League clubs to sign his first professional contract with Melbourne Heart along with fellow U-20 players, Kliment Taseski and Eli Babalj.

[6] In July 2021, after playing 20 games over two seasons with Western United, Hamill re-united with coach Tony Popovic, joining Melbourne Victory on a two-year deal.

[7][8] On 23 June 2022, Indian Super League club Mohun Bagan SG announce the signing of Brendan Hamill on a two-year deal.

[9] He made his debut for the club as substitute on 20 August against Rajasthan United at the 131st edition of Durand Cup; his team lost the match by 3–2.