He was selected as Melbourne's second pick and 15th overall in the 2004 AFL Draft. 2005 was a learning year for Dunn who developed well with Melbourne's VFL affiliate team, Sandringham.
The young forward made significant progress in 2006, increasing his body size, and worked hard to break into the senior lineup for his debut in Round Six, a tightly fought victory over the Cats. Dunn played eleven games at senior level, kicking 13 goals and showed promising signs that he will be a player of the future for the Demons.
He worked hard on his body over the pre-season and after suffering a fractured cheekbone in the VFL, Dunn was able to return to the senior team in round 4, kicking three goals in a heavy loss to the Dockers.
Dunn is looking to secure a regular place in the team after playing 12 games in the 2007 season.
Dunn was embroiled in controversy when reported twice within a minute for striking Brent Harvey - incidents for which he escaped from the tribunal with merely a reprimand.
In 2010 Dunn has switched from playing as a tagger to a defensive-forward and has kicked his most goals in a single season, including a career best five goals against Richmond at the MCG in Round 19.