The actor, best known for playing Carrie Bradshaw's gay best friend Stanford Blatch in the U.S. TV series, passed away aged 57 following a reported battle with cancer.
Shortly after news of his death broke, celebrities flooded to social media to share their memories of the screen star, with Cynthia among the first.
"So deeply, deeply sad we have lost @Willie.Garson," she wrote alongside a picture of herself with Willie on Instagram. "We all loved him and adored working with him. He was endlessly funny on-screen and in real life. He was a source of light, friendship and show business lore. He was a consummate professional - always. My heart goes out to his son, @Nathen_Garson. Nathen, I hope you know how much he loved you and how proud he was to be your dad."
Mario Cantone, who played Stanford's husband Anthony Marentino on the show, also paid tribute on Instagram. Alongside a snap of himself and Willie looking smart at a black tie event, Mario wrote, "I couldn't have had a more brilliant TV partner. I'm devastated and just overwhelmed with Sadness. Taken away from all of us way (too) soon. You were a gift from the gods sweet Willie. Rest …I love you."
Kim Cattrall, who starred in the original "Sex and the City" series and first two spinoff films but isn't involved in upcoming reboot "And Just Like That...", wrote on Twitter, "Such sad news and a terribly sad loss to the SATC family. Our condolences and RIP dear Willie xo"
And "Sex and the City" creator Darren Star told People of the late actor, "Willie touched all of us with his big heart and generous spirit. The man behind Stanford was a loving father, a mensch to his friends and radiated kindness to all. He is gone much too soon."
As well as his role in "Sex and the City", Willie was known for playing con man Mozzie in crime caper series "White Collar". Matt Bomer, who starred as the lead in the show and Mozzie's best friend, shared a tribute on Instagram, alongside a picture of himself with his late co-star.
"Willie. I don't understand. And it's not fair," he wrote. "This past year, you taught me so much about courage and resilience and love. I still haven't wrapped my head around a world without you in it- where I can't call you when I need to laugh, or be inspired. The last thing you did when we said goodbye was pull down your mask (I hate covid), smile, and wink at me."
"I know that it wasn't reflective of the pain you were going through, but it was indicative of everything you were and are to me: someone who lifted me up, who made me better, and who always, always made me smile. This also reminded me how strong our White Collar family is. We were all there for Willie, and for each other."
He concluded, "I love you forever Willie Garson. You live on in our hearts and minds always: and your White Collar family is always here for Nathen. Save a place for me, because you know I want to be at your table up there."