He suffered from several maladies after his hospitalization that included mini-strokes, the amputation of one of his legs, lung infections and more.
To mark the occasion, Kloots shared a few images on Instagram, as well as a loving message.
The post contained a photo of Cordero, as well as another photo of the Tony nominee cuddling up with his wife and son Elvis, who is now 1. Also included was a video of some loved ones singing happy birthday to Cordero during a celebration last year.
"My angel in heaven is celebrating his birthday today. Happy 42nd Birthday baby," Kloots wrote in the caption. "I bet you’re having quite the celebration up there, probably singing to everyone. Elvis and I will be singing here on earth to you"
The fitness guru explained that the pics were taken at a party at a friend's home last year.
"It could not have been a more perfect party for him. He was at his favorite bar with his favorite friends in Laurel Canyon, his dream come true," she said. "Right after he blew out his candles I remember him saying, 'Come on! I’m so blessed!'"
Kloots continued: "I love you with all my heart. Happy Birthday."
Fans of the stage star also sent the late actor well wishes for his special day.
"Happy Birthday to Nick!" said one in the comments. "All my positive thoughts to you and Elvis today."
"Happy Birthday to Nick. He is celebrating big with the almighty & he is probably telling God look I had the most amazing life partner ever!" wrote another. "Thinking of you & Elvis."
A third added: "Happy Birthday, Nick. While I never knew you, your legacy lives on through lovely Amanda and your adorable son, Elvis. The Heavens must be filled with music!"
Actress Selma Blair also shared a touching tribute in the comments.
Nick Cordero died in July after a long battle with coronavirus complications. (Photo by Walter McBride/FilmMagic)
"Happy birthday nick. If you weren’t born, and lived, and loved and noticed and lived your dreams. And found your love, your friends. Your boy. Your forever love and heart… then we would all be a little less full," said the 48-year-old actress, per Entertainment Tonight. "… Of watching the power of good and hope and caring and guts and talent unfold. And burn bright enough to light the dark spaces you left with your absence."
She continued: "I do not know you. But we all feel like we lost something big. But gained a lot more. With your memory. Too live on. And we all love Amanda and Elvis. Your friends and new ones. You did a great job here. I am just a witness but your family has become so beloved by more people. Through your connection. Your fight. Your life. Wherever you are… thank you rock star."
Cordero's birthday was also marked by the release of a live album from his performance at the well-known New York restaurant Feinstein's/54 Below. The album included a rendition of his song "Live Your Life," which was an anthem for Kloots and his fans throughout his battle with COVID-19.