The 58-year-old 'Die Hard' star and his wife Emma Heming-Willis became parents to Mabel on April 1, 2012, and they invited their family to join them for a bash to mark the tot turning one, reported E! online.
Rumer Willis, one of the actor's daughters with ex-wife Demi Moore, took to her Twitter to share her happiness.
"Today is my baby sister Mabel's 1st Birthday... Having a lovely day celebrating with my family (sic)," she posted.