The 263-171 vote was the second in a week, following its shock rejection of an earlier version on Monday.
The package is aimed at buying up the bad debts of failing financial institutions on Wall Street.
US President George W Bush praised lawmakers for their "spirit of co-operation" before signing the bill into law later on Friday.
The House adopted the new version after the Senate added about $100bn in new tax breaks to win Republican votes.
The Dow Jones Industrial Average had been buoyant ahead of the vote, surging up 250 points, but those gains were pared back amid profit taking and continued uncertainty, and it closed down 1.5%.