The allegations, involving an adult male, were reported to have happened in 1992
Prosecutors in Los Angeles are considering a sexual assault case against Kevin Spacey.
A spokesman for the city's District Attorney's Office said a case was brought to them last week and is under review.
The LA County Sheriff's Department said the alleged incident involved an adult male and was reported to have happened in October 1992.
It said it began investigating the allegations last December and presented its report to the district attorney last week.
It is unclear if California’s statute of limitations for sex crimes - which is normally 10 years – would apply.
It comes five months after Spacey was fired from Netflix political drama “House of Cards” over separate sexual misconduct accusations.
Actor Anthony Rapp accused him of trying to seduce him in 1986 - when Rapp was 14 and Spacey was in his mid-twenties.
Spacey later said he could not remember the incident, and apologised for any inappropriate conduct.
The Hollywood heavyweight also came under fire for using the occasion to publicly come out as a gay man for the first time.
More than 30 men have claimed they were victims of unwanted sexual advances by Spacey in the months since.
London’s Old Vic theater, where Spacey served as artistic director for 12 years, said it received 20 accusations of inappropriate conduct by Spacey between 1995 and 2013.