Lenz directed the Jackson, Michigan Civic Theater for two years before relocating to New York to seek work as an actor. In 1965 he made his Broadway debut in Mating Dance, starring Van Johnson. Though the show closed opening night, stage impresario David Merrick was in the audience, and soon afterward cast Lenz in the Broadway hit Cactus Flower as understudy for the juvenile lead role, Igor Sullivan. Lenz later took over the role and played it for a year. Film producer Mike Frankovich and Walter Matthau saw him in the part and cast him as Igor in the film version, with Goldie Hawn.
As of 2017, Lenz resides in Los Angeles with his spouse, Linda; the couple married in May 1982.[2] He has three children; sons Scott and Charlie, and daughter, Abigail.[2]