"101 today!!!! My darling Pappy on my knee. Happy Birthday to my wonderful, inspirational and loving father in law, Kirk. Love you with all my heart," the Oscar-winner wrote on Instagram. She included a photo of Douglas sitting on her lap.
Zeta-Jones also posted a photo of herself replicating a pose Douglas made in a 1957 photo in Cannes.
Fans of the the iconic Spartacus actor can get the best updates on his health by following Zeta-Jones, who frequently posts photos of her father-in-law. She's married to his son, Oscar-winner Michael Douglas.
Last month, Zeta-Jones posted a photo of Douglas and his wife, Anne, who is 98. The Chicago actress received the 2017 Anne Douglas Award at the annual Legacy of Vision Gala.
Photo: Instagram/ Catherine Zeta-Jones