The 27-year-old defender signed with the Mariners in October 2014 and has made 47 Hyundai A-League appearances in Yellow & Navy.
Poscoliero thanked the club and reflected fondly on his time at the Mariners.
“I'm saddened to be leaving such a great club and bunch of players, with whom I've made friendships with for life,” Poscoliero said. “I'd like to take this opportunity to thank the Central Coast Mariners and its fans, for the opportunity and fond memories.
“I wish the club all the success and I'm sure they will achieve great things,” Poscoliero said.
The Central Coast Mariners would like to thank Jacob for his services to the Club, and wish him all the best with his future endeavours.