The ex-Blue Peter and This Morning star, 54, is alleged to have committed the assault in Westminster in December 2008, when the complainant was 30.
Scotland Yard said Leslie, from Edinburgh, was charged with sexual touching of a woman by postal requisition on June 5.
He is due to appear at Westminster Magistrates' Court on July 25.
The Metropolitan Police said detectives continue to investigate.
John Leslie: Blue Peter star has been charged with sexual assault (Image: ITV • WENN)