Courtney was born and raised in Sydney, Australia. Courtney's big break came in 2010 when he played Varro in Spartacus: Blood and Sand. After being cast in Spartacus, he and Andy Whitfield became inseparable and remained so until Whitfield's death in 2011. Courtney remains close to Whitfield's wife and children.

He has also appeared in Jack Reacher Opposite Tom Cruise, and in A Good Day to Die Hard as the son of Bruce Willis's John McClane.