Aww — Leonardo DiCaprio has the biggest heart!

Shortly after the death of his What's Eating Gilbert Grape co-star Darlene Cates, the A-list actor paid an emotional tribute to the late actress.

"Darlene was the best acting mom I ever had the privilege of working alongside. Her endearing personality and incredible talent will live on in the memories of those who knew her, and those who loved her work," Leo, 42, wrote on Facebook. "My thoughts and prayers are with her family during this difficult time." Darlene and Leo portrayed mother-son pair Bonnie Grape and Arnie Grape, respectively, in the 1993 film.

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Leonardo and Darlene in 1993.

Darlene unexpectedly died in her sleep on Sunday, March 26, at age 69, her daughter, Sheri Ann Cates, confirmed in an emotional Facebook post.

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"It is with a bittersweet heart that we share that our precious wife, mother, and Gaga, Darlene Guthrie Cates, was called home, somewhat unexpectedly, peacefully in her sleep Sunday morning, March 26," the 51-year-old wrote.

"We take comfort in knowing that she is no longer in pain and is in the arms of our Heavenly Father, breaking away only to dance with our Savior, Jesus. (Dancing was something she talked about loving to do 'back in the day!')," Sheri Ann continued.

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Darlene and Leonardo in What's Eating Gilbert Grape.

Sadly, this isn't the first co-star Leonardo has had to pay tribute to. In late December 2016, he remembered his Growing Pains co-star Alan Thicke following his untimely passing.

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"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. I will be forever grateful for the opportunity I had to work with Alan early in my career," Leo wrote on the social media platform at the time.

"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," the Titanic star continued. "I miss him already. My thoughts and prayers are with the entire Thicke family during this difficult time."

Click through the gallery below to see the cast of What’s Eating Gilbert Grape then and now!