Del Piero, who missed last week's loss to Central Coast Mariners with a hamstring injury, ignited a dour first half with a brilliant individual goal in the 43rd minute before Ranko Despotovic made it 2-0 in the 45th minute.
But there was no sign of Del Piero after the break due to 'tightness', with Brett Emerton making his return from a leg injury in place of the skipper.
Harry Kewell was injected into the contest for the Heart in the 57th minute and missed a penalty shot nine minutes later after Joel Chianese handled the ball in the penalty box.
The Socceroos veteran atoned when he was involved in the lead up to Michael Mifsud's 72nd-minute goal as the Heart cut the deficit to 2-1.
Mifsud could have had two more goals but missed the target from close range in the 72nd minute and failed to control his first touch in the 75th minute to squander another guilt-edged chance.
The Heart continued to dominate, David Williams forcing three saves from Vedran Janjetovic in the space of three minutes.
The Sky Blues keepe also denied Golgol Mebrahtu from point-blank range in the 86th minute as the hosts held on for their sixth victory of the season to move to third on the A-League ladder.
The Heart battled bravely throughout but remain rooted to the bottom of the ladder on four points after their sixth loss this season.
It was a lacklustre start from both sides at the Heart successfully shut down the hosts who were badly out of sync in attack.
Ali Abbas and Despotovic both fired wild shots on goal but the Sky Blues created little else in attack before they were denied a strong shout for hand ball in the 33rd minute after the ball struck Massimo Murdocca's outstretched hand in the penalty box.
Del Piero took matters into his own hands with a brilliant goal two minutes from the interval.
The Italian maestro left two defenders sprawled on the ground and evaded two more with a jinking run before unlashing a shot that scorched past a helpless Andrew Redmayne in the Heart goal.
Despotovic doubled the lead in the 45th minute with a classy finish for his third goal in Sydney FC colours.
The Serbian received the ball with his back to the goal and spun to his left before unleashing a thunderous strike that beat Redmayne on his near post to send the hosts in with a 2-0 half-time lead.
Del Piero didn't emerge from the change rooms at half-time while Matt Thompson was replaced by Yairo Yau after a difficult first half.
Neither side fired a shot on target until Murdocca and Andrea Migliorini both forced saves from Janjetovic in the 55th minute in a sign of things to come.
Misfud finally broke the deadlock after a perfect pass from Mate Dugandzic but the Heart were unable to find the equaliser in a thrilling finish.
Sydney FC 2 (Del Piero 43, Despotovic 45)
Melbourne Heart 1 (Mifsud 75)