The Detroit News said Leonard and wife Christine separated earlier this year and Christine Leonard filed for divorce in May.
Documents filed in Oakland Circuit Court do not specify a reason for the split. The couple have no children.
Christine Leonard's attorney, Joseph Aviv, said a mediator has been appointed and a trial date of Dec. 12 set, the newspaper reported Thursday.
Court documents show Aviv requested a temporary restraining order against the 86-year-old author, barring him from making any changes in his life insurance or will or transferring assets. Elmore Leonard is also required to keep paying his estranged wife's personal expenses and maintaining their residences in Bloomfield Village, Mich., and Palm Beach, Fla.
Leonard has written 45 books, many of which are considered classics by fans of crime fiction. Several of his stories have been turned into films.