Organizers of the "Forward on Climate" rally also urged Obama to reject the controversial Keystone XL oil pipeline, designed to carry tar sands from Canada through several U.S. states.
USA Today said the march was billed as the largest climate rally in U.S. history. Organizers claimed 35,000 participants, though the newspaper said the size of the crowd could not be determined.
The group rallied at the National Mall before the march.
"This movement's been building a long time," Bill McKibben, founder of the environmental activist group said. " ... It's time for the president to stand up," he said. McKibben said the 1,000-plus mile pipeline was "one of the largest carbon bombs in history," the newspaper reported
The oil industry and its supporters say the pipeline would reduce U.S. dependence on foreign oil.
Obama's final decision on Keystone is expected soon. The pipeline would run from Alberta, Canada, with deliveries to several U.S. locations before reaching Texas refineries on the Gulf of Mexico.