Wagner, also a former city councilman, earlier said he would sit out the May 21 primary although he said he might run as an independent in the fall.
But following Mayor Luke Ravenstahl's announcement that he would not be running for re-election, he indicated that the situation has changed.
Wagner said in a statement Saturday that he's currently in Israel and hasn't completely assessed the situation in Pittsburgh. But he said "I am now looking at running in the primary."
The decision by Ravenstahl, Pittsburgh's youngest mayor, leaves councilman Bill Peduto and controller Michael Lamb as the only announced candidates.