The actor, who was appointed a UN representative on climate change in 2014, was pictured at the summit on Tuesday.
Leonardo DiCaprio has made an appearance at the Cop26 climate summit in Glasgow.
The Hollywood star, 46, was pictured at the conference surrounded by an entourage and wearing a blue suit featuring a colourful lapel pin.
He has worked on a number of documentaries about animal poaching and the environment, and was appointed a United Nations representative on climate change in 2014.
Kew Science, the research arm of Royal Botanic Gardens in Kew, said he had passed through its Carbon Garden space, where scientists will be highlighting the role plants can play in providing solutions to climate change across Cop26.
DiCaprio, who describes himself as an actor and environmentalist on Instagram updated his biography ahead of the event to include the hashtag #COP26
He also added a link to the United Nations website page on climate change.
In 2016, he was an executive producer on The Ivory Game, which examined the ivory trade.
Oscar-winning director Fisher Stevens also filmed DiCaprio as he travelled around the world to see the effects of global warming for the 2016 feature Before The Flood.