The actor penned a heartfelt tribute to his co-stars after their recent deaths.
Pratt co-starred with both men on all four seasons of Everwood; he played Bright Abbott, Beasley portrayed Irv Harper, and Williams starred as Dr. Andrew Brown.
"It's an incredibly sad season for the cast and crew of Everwood," Pratt acknowledged in his post. "We're still reeling from the loss of John Beasley and yesterday we lost Treat Williams as well."
Pratt continued by calling both men "exceptional actors, wonderful husbands, fathers and friends."
"They will be missed tremendously. I learned a great deal from working with each of them," he wrote. "The Beasley family and Williams family will be in my family’s prayers. May we see you again gentlemen."
"God bless you. Hug your loved ones. Reach out to that person that’s been on your mind," Pratt continued. "Life is fragile, precious and finite. Embrace it and one another."
Pratt concluded his post by suggesting fans watch some of Beasley and Williams' work, writing, "If you’re looking for some films to watch this week, check out Treat in Prince in the City, Hair, or Ten Things To Do in Denver When You’re Dead, and John can be seen in The Apostle, Walking Tall, and Rudy."
Beasley's son, Mike Beasley, confirmed that his dad died in May. His other son, Tyrone Beasley, later told The Hollywood Reporter that the actor had been undergoing tests for his liver when he took a turn for the worst.
"I lost my best friend today. They say you shouldn't ever meet your heroes because they don't turn out to be who you thought they were. That is so wrong. My hero was my father," Mike Beasley wrote on Facebook at the time. "Thank you for everything. I hope I made you proud. Love you more."
Two weeks later, Williams died after a Vermont motorcycle accident. He was airlifted to Albany Medical Center after the crash, and pronounced dead when he arrived, officials said during a press conference.
"I'm just devastated. He was the nicest guy. He was so talented. He was an actor's actor. Filmmakers loved him," Barry McPherson, Williams' agent of 15 years, told ET. "He's been the heart of Hollywood since the late 1970s. He was really proud of his performance this year. He's been so happy with the work that I got him. He's had a balanced career."