According to People, the Die Hard star and Heming are planning an intimate wedding on the Caribbean islands of Turks & Caicos later this week.
An insider claimed that Willis, who owns a home on the islands, has reserved a block of luxury hotel rooms and private villas near his property.
Willis, 54, has been dating the former Victoria's Secret model since last year. He was previously married to actress Demi Moore from 1987 until 2000 and briefly engaged to Baywatch star Brooke Burns in 2004.
Last October, Willis and 32-year-old Heming were reportedly spotted looking at engagement rings at the Cartier jewellery store in Los Angeles.
A representative for the actor has yet to comment.