Taking to Instagram, the "Basic Instinct" star posted a snap of himself and Catherine on their wedding day, writing alongside it, "Happy 20th Anniversary my darling! I love you always and forever @catherinezetajones."
Douglas also shared an audio clip detailing how he and Catherine met, revealing he was left mesmerized after watching her in 1998 movie "The Mask of Zorro".
"I'm watching this movie and then I say, 'Wow, who is this girl, she's incredible!' ' he recalled.
One month later, Douglas was attending the Deauville Film Festival in France when he found out the cast of "The Mask of Zorro" would be attending and asked his assistant to ask Catherine, if she was there alone, if she wanted to go for a drink.
And despite only being there for one night, Catherine agreed to go out with Michael, and also invited him to dinner with the film company.
"I probably made a big mistake when I looked at her and said, 'I just wanted to tell you, I'm going to be the father of your children,' " Michael laughed. "And she looked at me and said, 'I've heard a lot about you, I've heard a lot about you, I guess it's all true. Good night!' "
"I thought I had completely blown it but I'm happy to say, we remained contact and the rest is history!"
Meanwhile, Catherine shared a video montage of herself and Michael, writing alongside it, "20 years ago today Michael and I were married!! What an amazing magical night that was! And 7304.85 days and nights on, I love you now as I did then. ( except for the point 85 bit). Thank you for the love and laughter."
Catherine and Michael got engaged in December 1999, before marrying at The Plaza Hotel in New York in November 2000.