[citation needed] McMillan is a property sales consultant with TOOP+TOOP Real Estate in Hyde Park, Adelaide.

In 1998, he played "Ben Handleman" in his first feature film, Sally Marshall Is Not an Alien, followed by the role of "Tiny Maloney" in the television series 'Chuck Finn' for Seven Network in 1999.

He has performed in numerous theatre productions, including the role of "Jack" in Into the Woods by James Lapine and Stephen Sondheim, and "Vyasa" in the Mahabharata.

In 2012, McMillan appeared in the feature film Swerve, followed by the role of "Adauto Agallo" in the award-winning miniseries Mrs Biggs.

From 2013 to 2015 he filmed the Australian television drama Wonderland for Network Ten, in which he played "Carlos dos Santos".