The business mogul said the money would come from 100 per cent of the profits generated by his transportation and airline sectors.
It would then be invested in efforts to find renewable, sustainable energy sources in an effort to wean the world off oil and coal.
Branson's announcement came on the second day of the Clinton Global Initiative, an annual conference of business, political and non-profit leaders hosted by Bill Clinton, the former president, in New York.
"Our generation has inherited an incredibly beautiful world from our parents and they from their parents," said Branson at a press conference alongside Clinton.
"We must not be the generation responsible for irreversibly damaging the environment."
Clinton praised Branson, calling him one of the most "creative" and "committed" people he has ever known.
"We must not be the generation responsible for irreversibly damaging the environment"
the British billionaire
The commitment ensures that the conference, which works on solutions to global issues, would more than meet its goal of matching last year's efforts.
Branson said he would set up a renewable energy intitiative, Virgin Fuels, pledged around $400 million to the project over the next three years.
The first investment project of Virgin Fuels will be a California company called Cilion that will research on new kinds of ethanol production.
In 2005, the conference resulted in more than $2 billion in pledges.
Laura Bush, the US first lady, Pervez Musharraf, the Pakistani president and Hamid Karzai, his Afghan counterpart, are among those attending this year's event.