The 34-year-old striker joins the Jets as their marquee player - whose salary is exempt from the salary cap - after 62 appearances for England and a total of 516 Premier League matches, scoring 110 goals in a 17-year career.
In a significant signing for the developing A-League competition, Heskey, an FA Cup, League Cup and UEFA Cup winner, joins the Jets after playing for Aston Villa last season.
"This is an exciting new period in my life and I am looking forward to making a special contribution to the A-League and most importantly, to the Jets," Heskey said.
Jets CEO Robbie Middleby said the signing was a "fantastic result for the Jets and for the A-League".
"Emile has played our game at the highest level in England, both internationally and domestically, and he finished last season playing with Aston Villa in the English Premier League," he said.
"We are aware that Emile had other offers but he is genuinely excited to be a part of what we want to achieve at the Jets."
Coach Gary van Egmond was thrilled to have secured Heskey's services ahead of the new season kicking off next month.
"Emile is someone who has unbelievable experience, having played for England 62 times," van Egmond said.
"His effectiveness in being able to hold the ball up and invite other players to play off him is going to be a big benefit to us and is someone who can really lead the line."
Heskey played for Liverpool, Aston Villa, Birmingham City, Wigan Athletic and Leicester City in a long career in England, and he appeared in two FIFA World Cups™.
He joins Del Piero, 37, in the A-League after the Italian star opted for Sydney FC ahead of clubs including Premier League giants Liverpool on a two-year contract reportedly worth US$2 million a season.
Meanwhile, former German captain Michael Ballack has been linked with a move to A-League newcomers Western Sydney Wanderers.