Farina will take control of the Sky Blues for Sunday's clash with Melbourne Heart at Allianz Stadium.
The former Australian coach is in Papua New Guinea, but finalised a deal with the Sydney to replace Ian Crook, who stepped down from the position earlier this month.
Farina has been coach of Papua New Guinea since February 2011 after it was confirmed he accepted to manage the national side during the South Pacific Games in New Caledonia.
Farina’s last coached in Australia at the Brisbane Roar where he left in controversial fashion.
Farina was suspended indefinitely by the club over alleged drink driving charges and was later officially sacked on 14 October 2009.
Sydney FC chairman Scott Barlow said Farina had dealt with the demands of coaching a high profile team, which he will get with a Sky Blues side which includes Italian superstar Alessandro Del Piero.
"We believe Frank has the experience, leadership and coaching acumen to have a positive and immediate impact on Sydney FC," Barlow said in a statement.
"He also brings with him a wealth of A-League coaching experience that will serve him well as he joins us part way through our season."
The 48-year-old coached the Socceroos from 1999-2005, Brisbane Roar for three A-League seasons as well as Brisbane Strikers and Marconi in the defunct National Soccer League.
He was Socceroos coach for almost six years.
Farina takes over from caretaker coach Steve Corica, who will return to his role as an assistant.
"This is a fantastic opportunity," Farina said.
"There is a lot of attention on Sydney FC and I'm looking forward to getting to Sydney and working with the players and staff to create an environment where we can be successful on the pitch."
Farina was quick to air his thanks to his well-wishes, quickly tweeting after his appointment was announced.
"Thanks to the well wishes. Will try to respond later. To those who are not well-wishers, that's fine too. See you Sunday", Farina tweeted.