Garuccio, 30, has joined the Sky Blues on a two-year deal, following winger Abel Walatee in signing with the A-League Men powerhouse.
The full-back had signed a new two-year contract with United in July, but they were unable to register his contract due to a FIFA registration ban.
United were later placed into hibernation for the upcoming A-League Men and Women's seasons as they continue to fight both a court-imposed wind-up order and the withdrawal of their licence.
It meant all their players became free agents, with clubs clamouring to sign the best of the bunch.
Professional Footballers Australia (PFA) is also pushing for salary cap exemptions to allow players suddenly made jobless a chance to earn a career lifeline.
Garuccio had been keen to remain in Melbourne, and had interest from Melbourne Victory before eventually signing with Sydney.
"I'm really looking forward to this next step in my career," Garuccio said in a statement.
"Sydney FC's history of success speaks for itself, and I wanted to be part of that. I feel like I still have plenty to give and I want to make the most of the next two seasons.
"For me it's about contributing to a team that challenges for trophies.
"I believe my best football is still in front of me and I'm excited about what's ahead."
Garuccio won championships at Western and Melbourne City and also played at Adelaide United and Scottish clubs Hearts.
He will add valuable experience, creativity and leadership to the Sky Blues, who missed finals last season.
"Ben brings a good amount of experience and a winning mentality," coach Ufuk Talay said.
"He's a strong defender and influential going forward creating opportunities.
"He's a quality player and leader which will be important for us."
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