Winslet -- who was also nominated for her role in Steve Jobs but lost out to The Danish Girl's Alicia Vikander -- told ET earlier this month that she had Leo's back at the Academy Awards, and she stuck to that promise.
When DiCaprio finally won for Best Actor after being nominated five times prior, his Titanic co-star couldn't hold back her tears of joy. Cameras cut to the 40-year-old actress and her husband, Ned Rocknroll, looking proudly at the 41-year-old actor on stage (about 2:23 minutes into speech). "To my friends, I love you dearly. You know who you are," DiCaprio said.
While the actor didn't mention Winslet directly, he did use his win as a platform to speak about a cause close to his heart, the environment. "Making The Revenant was about man's relationship to the natural world," he declared. "Climate change is real, it is the most urgent threat facing our species."
The actor ended his speech on a thought provoking note, adding, "Let us not take this planet for granted. I do not take tonight for granted."
DiCaprio brought his mother, Irmelin Indenbirken, to the awards show, but on the red carpet, Winslet was his date! In addition to sweetly posing outside the event to the delight of Titanic fans everywhere, the famous friends were also super loving to one another inside the Oscars. The two were snapped hugging, exchanging sweet kisses on the cheek and holding hands.
Ahead of the Academy Awards, Winslet -- who won an Oscar for The Reader in 2009 with DiCaprio in the audience -- told ET that she was thrilled to see how many fans were in support of her longtime pal winning on Sunday night. "The sense of good will behind Leo is the thing that's touching me the most," she exclaimed. "I mean, literally, people in the street go, 'Hey Kate, you know it's Leo's year,' and I'm like, 'Hip, yeah! I think it really might be!'"