The Sky Blues had undergone a global, two-month search when Ufuk Talay left his post in March, but no candidate could eclipse Kisnorbo.
Former trophy-winning Melbourne City boss Kisnorbo was handed the interim role with four regular-season games left, but wasted no time in making the most of his A-League Men return.
After a hard-earned semi-final win over premiers Newcastle, the 45-year-old will coach just his seventh game at the helm of the Sky Blues - Saturday's grand final against Auckland FC.
This weekend's decider at Go Media Stadium in New Zealand will be the club's record-equalling eighth grand-final appearance.
Sydney are vying for a record sixth championship title, with the club confirming Kisnorbo's appointment on Tuesday.
"They've welcomed me like one of their own," Kisnorbo said.
"It's circumstantial, that things sort of happen in football.
"And since I've been here, they've made me feel very welcome, a part of the club.
"Nothing was too big or too small. When you have a club that does that for an interim coach and supports you, it's very humbling.
"I'm very grateful and honoured to be part of such a historic club."
Winning a championship will add an exclamation mark to Kisnorbo's ALM return after an ill-fated move to Japan.
Kisnorbo had moved to the J-League to be an assistant with Yokohama F. Marinos in 2024, after just seven games into a three-year contract with Melbourne Victory.
The ex-Socceroo then became Yokohama's head coach, but was sacked after just 10 games in charge.
In his short time at Victory, Kisnorbo - though disliked by fans for his time at City - took the club to the Australia Cup final.
Kisnorbo had guided City to back-to-back premierships (2021-22) and to the 2022 grand-final victory.
Sydney chair Jan Hendrik Voss viewed the appointment as a no-brainer.
"Patrick has impressed us enormously throughout the review process and during his time at the club," Voss said in a statement.
"He is a proven winner, he understands the A-League competition and the Australian and Asian football landscape.
"He has already demonstrated he can lift standards, performances and belief across the football club.
"We believe Patrick has the qualities to bring silverware to Sydney FC and we are looking forward to the Grand Final on Saturday."
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