The 31-year-old Australian has decided to leave the Latics and return to his homeland after being told earlier this month that his troublesome knee injury requires surgery that will keep him on the sidelines for at least one year.
Pogliacomi made 187 appearances in his two spells with the club.
He initially joined Oldham in 2002 and returned at the beginning of last season after a brief period with Blackpool.
A statement on the club's official website read: "Everyone connected with Oldham Athletic would like to wish Les all the best for the future as he prepares to head back to Australia."