The 30-year-old is Sydney FC's record scorer with 35 goals over five seasons and links up again with the Sky Blues after recently playing for Al Ain where he played in attack alongside Ghana star Asamoah Gyan.
Brosque, who has signed a two-season deal, was part of the Sydney side that clinched the Premiership and Championship double in the 2009/10 A-League season.
"It's great to have a crowd favourite in Alex back at Sydney FC. His leadership and his quality will be an important ingredient in our club this year," head coach Graham Arnold said.
Brosque, who was passed over for Australia's FIFA World Cup™ squad, has played 21 times for the Socceroos with five goals.