In a Facebook post Wednesday, DiCaprio, whose first significant role was as homeless teen Luke on the seventh season of Growing Pains, fondly remembered Thicke, writing that "no one was cooler" than the actor.
"Alan was a devoted father, husband, friend and role model. He knew how to harness the power of the entertainment industry to be a positive influence in so many lives - including mine," DiCaprio wrote.
"I will be forever grateful for the opportunity I had to work with Alan early in my career. He had tremendous class, a huge heart, and he taught me and so many others the valuable lessons about humility and gratitude. I've seen him a number of times over the years and when Alan Thicke walked in the room, quite frankly, no one was cooler. I miss him already - my thoughts and prayers are with the entire Thicke family during this difficult time."
Thicke's son, singer Robin Thicke, remembered his father as "the greatest man I ever met" and "always a gentleman," he told the Los Angeles Times.
"The good thing was that he was beloved and he had closure," Robin said of his father. "I saw him a few days ago and told him how much I loved and respected him."
Actor Kirk Cameron, who played Thicke's son Mike Seaver during seven seasons of Growing Pains, also paid tribute to his "TV dad" on Instagram.
"I spent Monday through Friday for seven important years with Alan Thicke as my 'TV dad,'" Cameron wrote. "I'm shocked and truly heartbroken today at the news of his death. Alan was a generous, kind and loving man. I am so blessed to have grown up with him."