Heskey was available on a free transfer after leaving Aston Villa at the end of last season and he had been linked with a move to Hull City among other clubs.
However, the 34-year-old has opted for a fresh challenge down under and he has become the Jets' marquee signing for the 2012/13 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 told his new club's official website.
"I hope I can help grow football at the grassroots level and also provide advice to young players at the Jets.
"The season isn't far away, so I will be in Newcastle soon, training with my new team-mates and be ready for kick off on October 7."
Heskey joins former Sunderland forward Michael Bridges at the Jets and coach Gary van Egmond is delighted with the capture.
"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.
"He's someone who can really lead the line and is exactly what we've been missing."