Austin said: "I'm delighted to be joining Brisbane Roar.
"To play abroad is something I've always wanted to do and when the opportunity came up to join this club I was looking to explore it.
"I met the gaffer Warren [Moon] in London and he sold me the project of the football club and it was one I was excited about!
"I want to help the club get back into the top six and on a personal note score as many goals as possible."
It was announced that Austin had signed a 'multi-year' deal.