[6] In 2004 he succeeded George Gregan as ACT Brumbies Captain and played every game that season except the final due to injury and thus was unable to lead the team to claim the Super 12 title that year.

He scored a sideline penalty goal in 2000 against South Africa in Durban to win Australia's first Tri Nations crown.

[8] Mortlock won man-of-the-match and had an 80-metre intercept try at then-Telstra Stadium to help knock the All Blacks out of the 2003 Rugby World Cup in the semi-final.

Australian Rugby Union CEO John O'Neill endorsed this decision saying that Mortlock is a "real captain courageous" and an "inspirational leader".

[2][11][12] Mortlock was declared the Rebels inaugural Captain on 2 February 2011,[13][14][15][16][17] with former Wales international Gareth Delve as Vice-Captain.

In June 2012, Mortlock announced he would retire as a player at the end of the 2012 Super Rugby season,[6] However, in 2013 he continued with the Rebels in a supporting role.