The Hotel Rwanda actor first teamed up with the U.N. last year (09) to front its climate change campaign, urging world leaders to sign a treaty limiting greenhouse gas emissions.
Cheadle's efforts have won him high praise from organisation officials and he will be promoted to a Goodwill Ambassador during a special ceremony next month (Jun10).
He says, "I will be named officially in Rwanda on June 5th, a Goodwill Ambassador for the United Nations Environmental programme. I'll be in Rwanda on June 5th."
Cheadle's philanthropy work does not stop there - he is also a key voice in the call for an end to the genocide in Darfur, Sudan, establishing the Not On Our Watch charity with his Ocean's Eleven co-stars George Clooney, Brad Pitt and Matt Damon.