Kisnorbo was recommended to Hearts by Jambos legend Dave McPherson after impressing with South Melbourne.
The 23-year-old becomes Hearts' third new signing of the summer following the arrivals of Dennis Wyness and Paul Hartley.
Kisnorbo was excited at the prospect of playing in the SPL next term.
"Even just to play in the Scottish Premier League was a big incentive to come here and its even better to have the chance to play in the Uefa Cup," said Kisnorbo
"I knew that Hearts were a big club before I came here, but I was shocked when I realised just how big when I first arrived.
"You have to believe in your own ability and I will be looking to do my best in the SPL and Europe."
