Dunstall was born and raised in Brisbane. He attended the Anglican Church Grammar School from 1977 to 1981. At school he played soccer as a goalkeeper and also rugby union. His junior Australian rules football was spent playing with the Coorparoo Football Club in the then Queensland Australian Football League. In 1984, as a 20-year-old, Dunstall claimed the QAFL leading goalkicker award with 73 goals in the home and away season and kicked seven goals in a grand final winning side for Coorparoo.

Dunstall was recruited by the Melbourne-based Hawthorn Football Club who were looking for a “stay at home” type full-forward and he made his VFL/AFL debut in the league in 1985.

1988 was a special year for Dunstall. In Round 19 against Fitzroy he brought up his first century of goals in a season. He had kicked 98 goals going into the match, and Hawthorn supporters expected the required two goals to come sooner rather than later. However, Dunstall would miss his first two shots and drop a few marks before putting through his first goal at the 17-minute mark. The moment of truth came at the 30-minute mark of the first quarter when teammate Dermott Brereton kicked the ball high into the air. It took a vicious bounce over Fitzroy defender Brett Stephens’ head and landed in Dunstall’s arms. The goal was kicked and the fans came running onto the ground to congratulate only the second Hawthorn player after Peter Hudson to kick 100 goals in a season. Dunstall kicked a further six goals for the game to finish with 8 goals. He would finish the home-and-away season with 124 goals, winning his first Coleman Medal. He also won his first club best and fairest award. In the 1988 Grand Final massacre against Melbourne, he kicked 7 goals.

1990 began promisingly enough for Dunstall. In Round 1, in the Grand Final rematch against Geelong at Waverley Park, he kicked a then career-best 12 goals after being held goalless in the first quarter. Hawthorn went on to thrash the Cats by 115 points. In Round 4 against Brisbane Bears at Princes Park in wet conditions, Dunstall kicked 8 goals, bringing up his 500th career goal in the process, as the Hawks won by 82 points. But in Round 9 against Melbourne, Dunstall was injured in the first quarter. He fell heavily on an opponent’s boot and sustained a serious injury at the front of his head. He was taken from the ground and admitted to The Alfred Hospital. At that stage of the season Dunstall had kicked 41 goals. The injury would cause him to miss the next four matches. After his return in Round 14, he kicked a further 42 goals, including 11 goals against Collingwood in Round 20. On the Footy show after the 1990 AFL Grand Final, Leigh Matthews said that he was glad Hawthorn got knocked out of the finals, because Dunstall always seemed to kick a huge number of goals against the recently crowned premiers.

Dunstall kicked 82 goals in 1991, including 6 in the Grand Final as Hawthorn claimed their 9th Premiership. They were unable to defend the premiership in 1992 after they lost to West Coast in a closely contested Elimination Final. But Dunstall enjoyed arguably his most successful season on an individual level. He won his third Coleman Medal after kicking 139 goals during the home-and-away season (six more in the Elimination Final took his season tally to 145), and finished second in the Brownlow Medal vote count. In Round 7 Dunstall kicked what would be his career best of 17 goals against Richmond, just one goal short of the record held by Fred Fanning of Melbourne. Dunstall reached his century of goals against Geelong in Round 16 at Kardinia Park with his fifth goal of the match just before half-time. He ended the match with 9 goals and beat three opponents as Hawthorn won by 19 points. Dunstall’s outstanding season was recognized with his third club best and fairest award, as well as his first selection in the All-Australian team at full-forward.

In the Elimination Final in 1996 against Sydney, Dunstall tumbled over Andrew Dunkley and was left writhing on the ground clutching a badly injured knee which required a knee reconstruction. Surprisingly, Dunstall’s knee healed well enough for him to play half a reserves match just before the start of the 1997 AFL season, and was picked to play against St Kilda in the opening round.

In 2002 Dunstall was inducted into the Australian Football Hall of Fame.

In 2004 Dunstall held the position of interim CEO at Hawthorn,. After handing over the CEO position Dunstall remained on the Hawthorn board until the end of 2013 when his term expired. He currently works on radio station Triple M as a commentator. His stint as CEO led to the nickname of “The Chief”. His mannerisms on Fox Footy and Triple M lean towards professionalism, which at times can be seen as too serious (as on the 80’s Heritage Round episode of The AFL Footy Show on 20 July 2006.) He has been the focus on continual baiting by his Triple M co-commentators and is nicknamed “The Ugandan National Symbol” for his gorilla-like style, attitude and demeanour. These gorilla references made their way onto The Footy Show, where both fans and Sam Newman repeatably baited Dunstall with video clips and props.

Reflecting his Queensland upbringing, Dunstall is depicted lining up for goal wearing a Queensland state guernsey in Jamie Cooper’s painting the Game That Made Australia, commissioned by the AFL in 2008 to celebrate the 150th anniversary of the sport.

In July 2014, Dunstall was elevated to legend status in the Hawthorn Hall of Fame.