Antonis, 19, is set to represent Australia at the Under-20 World Cup next week, and will follow in the footsteps of Socceroos Vinnie Grella and Marco Bresciano in heading to Parma.
 
Sydney chief executive Tony Pignata said Antonis' departure is the first step in what is set to be a flourishing career for the Young Socceroo.
 
"We have come to an agreement with Parma that we are satisfied with and Terry can now look forward to the next chapter of his career," Pignata said.
 
"Terry joined Sydney FC as a 16-year-old and has matured into a player that has been able to move to one of the best football leagues in the world where he can hopefully further develop his game and go on to serve the Socceroos for years to come.
 
"We wish him every success at Parma and for the rest of his career. We would love to have him back at Sydney FC one day in the future."
 
Antonis follows in the footsteps of A-League youngsters that have departed for European shores this off-season, including Marco Rojas (21, Stuttgart), Mat Ryan (21, Club Brugge) and Ben Halloran (20, Fortuna Dusseldorf).
 
The midfielder played 39 times for the Sky Blues, for one goal. He remains the youngest player to play for the club after debuting aged 16 in 2010.