"Today the American people can be proud because this historic agreement is a tribute to American leadership. Over the past seven years, we've transformed the United States into the global leader in fighting climate change," Obama said.
He said the accord shows what is possible when the world stands as one, adding: "This agreement represents the best chance we have to save the one planet that we've got."
Speaking at the White House hours after the deal was completed, Obama said that "no agreement is perfect, including this one," and that negotiations that involve nearly 200 nations are always challenging.
"Even if all the initial targets set in Paris are met, we'll only be part of the way there when it comes to reducing carbon from the atmosphere," Obama added.
Obama has made combating global climate change a top priority of his presidency but has encountered stiff resistance to his proposals from Republicans in Congress.
Republican Jim Inhofe, a global warming skeptic who heads the Senate Environment and Public Works Committee, said the climate deal was "no more significant to the United States" than the 1997 Kyoto Protocol, the last major climate deal.
Unlike the Kyoto pact, forged with Democratic President Bill Clinton in office, the Paris agreement will not be a fully legally binding treaty, which would almost certainly fail to pass in the US Congress.
Clinton's White House successor, George W. Bush, concluded that the Kyoto pact was giving big emerging economies such as China and India a free ride, and would cost US jobs. Having signed the deal, Washington never ratified it.
"Senate leadership has already been outspoken in its positions that the United States is not legally bound to any agreement setting emissions targets or any financial commitment to it without approval by Congress," Inhofe said.
Besides Inhofe, few Republicans voiced their opinions on the deal.
None of the top Republican presidential candidates nor Republican leaders in Congress had commented on the deal on Twitter as of 6:00 pm Eastern (1100 GMT) Saturday.
Previously, Republican presidential front runner Donald Trump has cast doubt on science that attributes the warming of the climate to carbon emissions, saying the world's temperature "goes up and it goes down."
Democratic presidential front runner Hillary Clinton released a statement via Twitter applauding the agreement and pushing back against its critics.
"We cannot afford to be slowed by the climate skeptics or deterred by the defeatists who doubt America's ability to meet this challenge," Clinton said, vowing to make climate change a top priority if elected president.
Representative Raul Grijalva, the top Democrat on the House Committee on Natural Resources, urged quick action by the Republican-led Congress to fund and support the Paris accord.
"Too many people have spent their careers pretending that climate change is a hoax perpetrated by shadowy environmental groups and Machiavellian research scientists," Grijalva said. "The American public knows full well that's not the case."