The US House of Representatives has passed the $700 billion financial bailout plan by 263 votes to 171 votes and it was almost immediately signed into law by President George Bush.
Welcoming the vote, President George Bush said the US had shown the world it would stabilise its financial markets and maintain its leading role in the global economy.
The measure represented "decisive action" to ease the credit crunch facing the economy, he said.
President Bush signed the Emergency Economic Stabilization Act of 2008 in the Oval Office at the White House this evening.
House Speaker Nancy Pelosi said that faced with a situation that had "terrible ramifications", Republicans and Democrats had worked in a bi-partisan way to bring the legislation rejected last week back to the floor.
Federal Reserve Chairman Ben Bernanke said the US central bank will do whatever it can to combat the credit crisis and help the economy.
"We will continue to use all of the powers at our disposal to mitigate credit market disruptions and to foster a strong, vibrant economy," Mr Bernanke said in a statement.
Mr Bernanke said the bill was a critical step toward stabilizing financial markets and ensuring a freer flow of credit. He said it demonstrated the US government's commitment to "do what it takes" to support the economy.
The package contains provisions favored by House Republicans, including $149 billion in tax breaks, a higher limit on federal bank-deposit insurance and changes in securities law. It also restates securities regulators' authority to suspend asset-valuing rules that corporate executives blame for fueling the crisis. The Senate approved the bill Wednesday 74-25.
House Majority Leader Steny Hoyer and the Republican leadership had signaled their confidence in advance that the measure would pass.
Additional reporting: Reuters