DiCaprio is best friends with actor Tobey Maguire, whom he beat to get roles in Roseanne and This Boy's Life.

He has been linked to Emma Bunton, Naomi Campbell, Helena Christensen, Sara Foster, Bridget Hall, Natasha Henstridge, Eva Herzigova, Bijou Phillips, Alicia Silverstone, and Amber Valletta. Leonardo dated Brazilian supermodel Gisele Bündchen from 2002 to 2005. Since 2006, however, he has been dating Israeli international supermodel Bar Refaeli.

DiCaprio sued Playgirl magazine to stop the New York-based monthly magazine from publishing unauthorized nude photos of him in its July 1998 issue. Some reports claim the photos were secretly taken while the actor was lounging in the nude, while others say they came from stills of his nude scenes in, or from outtakes of, the movie Total Eclipse. The case was settled on June 29, 1998 for an undisclosed amount.

A registered Democrat in California, DiCaprio has been active in promoting liberal causes, and in 2004 supported Senator John Kerry's presidential campaign.

A committed environmentalist, DiCaprio has received praise from environmental groups for opting to fly on commercial flights instead of chartering private jets, which use more fuel. He has also mentioned that his house has solar panels, that he owns three Toyota Prius cars, and has bought hybrids for family members.His actions have inspired other celebrities, such as Orlando Bloom and Penelope Cruz. In an article in Ukula about his new film "11th Hour" (which he co-wrote, co-produced and narrated), DiCaprio cites global warming as "the number one environmental challenge."

In 1998, he and his mother donated $35,000 for a state-of-the-art "Leonardo DiCaprio Computer Center" at the Los Feliz branch of the Los Angeles Public Library (1874 Hillhurst Avenue) which happens to be the site of his childhood home. It was rebuilt after the 1994 Northridge earthquake, and opened in early 1999. There are commemorative placards and curious fans are welcomed at the library.