Vidosic, who worked with Farina at Queensland Roar from 2006-2009, was considered a key part of the coaching team that took Roar to consecutive championships in 2011 and 2012.
Last season he took over from Ange Postecoglou in the Roar head coach role, before stepping aside for Mike Mulvey in December,to take on a broader technical role that incorporated Bakrie Group football interests in Europe, South America, Asia and Australia.
'I’m delighted to be joining Sydney FC and to be working together again with Frank," Vidosic said.
'There is a great potential at Sydney FC and I hope to work extremely closely with the players and help them make the most of their ability.
'We have a very strong and talented squad and I expect us to be challenging for honours this season."
Farina said he looks forward to reunited with Vidosic.
'It’s great to be able to bring Rado to Sydney FC," he said. 'Having worked with him before I know he is a first class coach and will give the squad an extra influence.
'He has a real analytical and tactical brain and is very experienced in bringing the best out players."
Vidosic will take care of first team assistant coaching duties with Steve Corica appointed Sydney FC’s National Youth League team coach.
'Rado has a great track record and knows exactly what it takes to win an A-League Championship," Sydney FC Chief Executive Tony Pignata said.
'We are delighted to have him on board and I believe his knowledge and tactical expertise will help Sydney FC achieve success on the pitch this season."