The 'Diehard' star and his 35-year-old model wife, who are already parents to daughter Mabel, 21 months, recently returned from a romantic trip to the Turks and Caicos Islands, where the 58-year-old actor owns a home.
An insider told UsMagazine.com: "The babymoon was at Bruce's place in Parrot Cay."
Emma posted a photograph of herself looking happy and relaxed on the beach during their holiday on her Facebook page with the caption: "#BabyMoon 2014 Photo: B. Willis"
She also shared a picture of her famous husband flying a kite on the beach and wrote: "A man with many hidden talents #KiteFlying"
It was first revealed in December that the couple, who married five years ago, are expecting another baby.
Bruce also has three daughters, Rumer, 25, Scout, 22, and Tallulah, 20, with his ex-wife Demi Moore, and the source suggested the actor wouldn't mind having another baby girl.
The insider said: "[Bruce is] adorable with Mabel and all of his girls. It's hilarious to see the tough guy stereotype just melt away. He'll put on a baby voice, get cute with her. Being a dad is no doubt the most important thing for him."
Emma appears to be equally close to Bruce's other daughters as shortly after returning from their holiday, the couple helped Tallulah celebrate her birthday in New York City.
The brunette beauty shared a photo of her youngest stepdaughter on February 3, with the caption: "So proud of the woman you're becoming. Thank you for allowing me into your world. Happy Birthday @buuski #proudstepmom"