The 22 year-old was born in Perth, Australia to Scottish parents and is eligible to represent either country at international level.
However, Herd has decided to play for the Socceroos and the news will come as a big boost to Australia manager Holger Osieck, who is keen to add more depth to his pool of players.
"Obviously Australia is my country; it's where I've grown up, it's where I'm from. I want to play for Australia," he told Fox Sports FC.
"It's every kid's dream to play for their country and if I get the chance I'll be honoured."
Herd signed with Villa as a 15-year-old in 2005 and had represented Australia at Under-20 level.
Scotland manager Craig Levein was believed to have kept close tabs on the full-back before he made his decision.
Source: Team Talk