A committed environmentalist, DiCaprio has received praise from environmental groups for opting to fly on commercial flights instead of chartering private jets. He has also mentioned that he drives a hybrid car and that his house has solar panels. His actions have inspired other celebrities, such as Orlando Bloom and Penelope Cruz. In an article in Ukula about his 2007 film 11th Hour (which he co-wrote, co-produced and narrated), DiCaprio cited global warming as "the number one environmental challenge." DiCaprio and former vice-president Al Gore announced at the 2007 Oscar ceremony that the Oscars had incorporated environmentally intelligent practices throughout the planning and production processes, thus affirming their commitment to the environment. On July 7, 2007, DiCaprio presented at the American leg of Live Earth. During the 2004 Presidential election, DiCaprio campaigned and donated to John Kerry's presidential bid.

In 1998, DiCaprio 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.

During the filming of Blood Diamond, DiCaprio worked with 24 orphaned children from the SOS Children's Village in Maputo, Mozambique, and was said to be extremely touched by his interactions with the children.

He was invited to the Scottish Parliament at Holyrood in Edinburgh, Scotland, to talk about his environmental foundation to teach people about global warming. It is not yet known[when?] if he has accepted the offer, due to his busy schedule in Hollywood.

FEC showed DiCaprio gave $2300 to Barack Obama's presidential campaign in the 2008 U.S. Presidential election, the maximum contribution an individual can give in an election cycle.

In 2010, he donated $1,000,000 to relief efforts in Haiti after the earthquake.

Also in 2010, DiCaprio's environmental work earned him a nomination for VH1 Do Something Awards. The awards show, produced by Vh1, is dedicated to honoring people who do good and is powered by Do Something, an organization that aims to empower, celebrate, and inspire young people.