A product of Floriana FC, he made his Premier League debut in season 2004/05 and apart for a short spell with Lija Athletic, he played for the Greens until being transferred to Hamrun Spartans in summer 2008.
Micallef spent two years with the Spartans before returning to Floriana in summer 2010.
Meanwhile apart from Justin Haber and Danial Mitev, Mosta have also secured the services of Gozitan central defender Ferdinando Apap.
Apap played for Ghajnsielem before joining the Sheffield FC Academy.