Hudson shared a photo of herself with Bellamy, 37, calling the photo "ExMas."
"From our #ModernFamily to your #WhateverKindaFamilyIsYourKindaFamily," the actress said, referencing the hit ABC comedy. "We send you much love and blessings on this Christmas eve #ExMas #HolidayFun #SantasComing."
Hudson, 36, split with the Muse frontman in 2014 after four years together. They became engaged in April 2011 and three months later welcomed their son, Bing. Hudson also has a son, Ryder, 11, with Black Crows frontman Chris Robinson.
Hudson told Harper's Bazaar last month that "it's nice" being single.
"I'm at that age now. I really do feel very lucky," she added. "I've had my kids and my relationships. I've set my life down -- I'm in my house, and I'm alone with my children -- and I'm at peace, and that's a really nice feeling. All I really want in my life is to maintain that."