The France international has filed a "multi-million-pound" claim with the Employment Tribunal, seeking the return of pay up until the end of his contract with the English champions, which ended in June.
Mendy was found not guilty of one count of rape and one of attempted rape by a British court in July after being acquitted of six counts of rape and one count of sexual assault in January following allegations made by multiple women.
Mendy's lawyer Nick De Marco confirmed he was acting for Mendy in a "multi-million pound claim for unauthorised deductions from wages" in an emailed statement to Reuters.
"Manchester City FC failed to pay Mr Mendy any wages at all from September 2021, following Mr Mendy being charged with various offences all of which he was subsequently acquitted of, until the end of his contract in June 2023," the statement added.
The club declined to comment when contacted by Reuters.