He has played U21 football for Ireland but has opted to pursue his international career with Australia.
Boss Paul Sturrock said: "Defensively, we are very short and we need to make sure we have players coming in.
"He has got real potential and he wants to do well. He has played with Alan Judge and Cillian Sheridan in the Republic of Ireland Under-21 side, and they have waxed lyrical about him.
"Our scouts have also given us some very good reports, so he is a welcome addition."