DiCaprio, 41, participated in an investment round, which includes Marlon Wayans, Adam Rodriguez and professional tennis players John Isner and Steve Johnson.
Channing Tatum was an early investor.
Runa products are made from guayusa caffeinated tea leaf from the Ecuadorian Amazon, which is sustainably produced in the rainforest by 3,000 indigenous farming families.
"I am so proud to join with Runa in supporting the indigenous people of the Amazon," DiCaprio said.
"The future of these communities, and many like them across the world, are at risk as their native lands are exploited for natural resource and agricultural development. Sustainable farming practices are key to helping ensure a brighter future for so many local people."
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"We must all do everything we can to help indigenous and local people who too often suffer the worst environmental degradation, and are most at risk from climate change," he added.
"Empowering them to stand up and fight back against the outside interests that threaten their survival is a cause that must be championed."
DiCaprio joins World Wildlife Fund President Yolanda Kakabadse and Former US Secretary of Agriculture and Executive Director of UNICEF Ann Veneman on the company's advisory board.