The 24-year-old, who will begin training with the Panthers next week, played 154 games for Leeds after making his debut for the Super League club in 2011.
In 2015 Hardaker was named Man of Steel after helping Leeds win the Challenge Cup, League Leaders Shield and First Utility Super League Grand Final.
"This is truly exciting for the Panthers to have a current English international joining the club for the remainder of the 2016 season," Panthers Executive General Manager Phil Gould AM said.