However, the LA district attorney's office decided not to file charges after she "declined to be interviewed by the investigating officer".
There is a second case still pending against Spacey in the L.A. County Sheriff's Department.
Spacey's case, involving an adult male in 1992, was presented to the district attorney's office in April and had been under review.
The accusation against Seagal, who has faced multiple allegations of sexual misconduct over the years, stemmed from an alleged sexual assault in 1993, the statute of limitations for which reportedly expired in 1999.
Word of the "declinations", as they are called (because prosecutors decline to press charges), arrived in a statement emailed to USA TODAY from Greg Risling, the spokesman for the task force.
Off the hook: The Los Angeles County District Attorney's office has declined to press charges against Anthony Anderson for an alleged 2017 assault.More news: Serena Williams Wins US Open Match In Tutu Following Catsuit Ban
Spacey and Seagal are facing potential charges in other cases now under investigation.
There are no tears shed by Robin Wright's Claire Underwood in the latest House of Cards teaser, which confirms that Kevin Spacey's Frank Underwood is being killed off in the Netflix drama's sixth and final season.
It's not unsurprising given that Spacey and Cards parted ways after sexual misconduct claims against the actor surfaced last fall.
The two-time Oscar victor has been accused of sexual misconduct by at least 15 men, with alleged incidents spanning his decades in film and on the stage. Since then, several men have come forward to report incidents involving the actor.
Mr Spacey claimed to have no memory of the events but publicly apologised.