Kisnorbo, 32, was a free agent having left Leeds United at the end of the last season following four seasons at Elland Road.
Heart have lost marquee signing Orlando Engelaar to a fractured leg for up to six months, prompting Aloisi to consider shifting Patrick Gerhardt from the centre of defence to a holding midfield role.
"In addition to being an excellent defender, Patrick brings tremendous leadership qualities and competitiveness to our defensive half," Heart coach Aloisi said upon unveiling Kisnorbo on Tuesday.
"Anyone who has followed the Socceroos appreciates the energy and fearlessness with which Patrick plays and his all-round game means he can partner with anyone in central defence.
"Having him in the squad strengthens our spine and provides me with a number of tactical options."
Also a full Australia international, the last of Kisnorbo's 18 appearances for the Socceroos came in 2009, with his career for club and country interrupted by a serious Achilles injury in March 2010.
