Carrusca had been on trial with the club since ending his five-season stint with Adelaide United but is now officially on their roster and is expected to play some part in Wednesday's FFA Cup quarter-final against Sydney FC.
The 34-year-old's contract fits under the salary cap, meaning City still have scope to bring in one more marquee player to complement injured skipper Bruno Fornaroli.
Fornaroli jumped the gun last month unveiling the Argentinian as City's new signing on Twitter, before deleting his tweet.
Fornaroli tweeted a picture with his fellow South American, writing "WELCOME TO THE FAMILY!" alongside the Argentinian and Uruguayan flags.
On Tuesday he was again quick to tweet a picture of his new teammate.
Crucially, Carrusca will not be counted as a foreign player as he became an Australian citizen in July.
"Obviously we know a lot about his talent and his ability, his assists and goals," coach Warren Joyce said.
"What's really impressed me about him is as a human being, a man - the way he comes into the club and conducts himself is a great example to the younger players at the football club.
"He's a good pro who's genuinely just here because he wants to play football.
"He's missed a lot of pre-season so we've got to build him up ... (I'm) looking forward to getting him and seeing him fully fit."
City also handed a senior contract to striker Braedyn Crowley after the 20-year-old signed a scholarship deal with the club last year.
Originally from Townsville, Crowley has previous A-League experience with the Newcastle Jets and has played in NPL Victoria with Northcote City.