The 39-year-old striker moved to Australia in 2012 after his 19-year career with Serie A giants Juventus came to an end.
The former Italy international has insisted that he has not made a decision over his future yet.
"Australia, the moment has arrived to say arrivederci. My adventure with Sydney FC is about to be concluded, and, even if it makes me rather sad, because I have had a wonderful time here," Del Piero said in a statement.
"The moment has arrived to make some changes. I am well aware that I have given a lot and received even more. Now I just need some time to think over all the prospective opportunities for my future."
Del Piero hinted earlier this month that he would consider a return to Juventus.