Molloy has made 40 appearances for the Wildcats since joining from Huddersfield in April 2013.
Meanwhile, centre Bill Tupou will also miss Saturday's Challenge Cup semi-final at Warrington after suffering a minor tear in his hamstring.
"The injuries are a loss but we've got depth in the squad," head coach Chris Chester told BBC Radio Leeds.
Wakefield Wildcats second-row forward Jon Molloy will be out for four weeks after suffering a torn pectoral muscle.