The 229-197 vote, along party lines, came after a partisan House debate over changes needed to the landmark 1996 welfare overhaul.
The bill forces states to put many more welfare clients into work, and each person would have to work more hours than required before. The measure also provides hundreds of millions of dollars to promote marriage and sexual abstinence.
Earlier, the House rejected a Democratic alternative that would have provided billions more for child care, opened aid to legal immigrants and let states put welfare moms in education and training programs.
Democrats are now looking to the Senate, where moderates from both parties are working on compromise legislation.
With the welfare rolls cut by more than half, Republicans dismissed Democratic critics, saying their predictions of disaster were wrong in 1996 and will be wrong again.
"The Democrats, quite frankly, simply have no ground on which to stand, other than to applaud the success of welfare reform, which they refuse to do," said Majority Leader Dick Armey, R-Texas.
Republicans displayed a series of posters in the House chamber quoting Democratic critics from 1996, mocking their warnings about cutting guaranteed federal aid.
"Take a good look at where we were six years ago and where we are today," said Rep. Deborah Pryce, R-Ohio.
Rep. Ben Cardin, D-Md., said that argument made no sense, given that Republicans are proposing significant changes to the 1996 law. "We're defending the current law. They're trashing it," he said.
Democrats also want more money for child care, saying there is not enough now and even more will be needed if more single moms are forced to work. And, unlike Republicans, they want to restore benefits for legal immigrants, who were cut off in 1996.
The Republican bill, which closely mirrors President Bush's plan, includes up to $300 million for experiments promoting marriage and continues to bar legal immigrants from aid programs for their first five years in the United States.
Republicans have made a few moves toward the Democratic position since Mr. Bush released his plan. They added $2 billion over five years for child care, an area for which the president did not at first propose adding any new spending.
The GOP made the reduction of poverty an explicit goal of the welfare program, a symbolic move meant to signal that just leaving the rolls and remaining poor is not good enough.
Action on the legislation stalled throughout the day Wednesday over a provision that let states skirt rules and merge a variety of aid programs, including housing, food stamps and child care.
Republicans on the House Appropriations Committee objected to the experimental program, saying they did not want their spending decisions to be ignored. That led other committees to demand that money for their programs remain intact too. So the bill was rewritten to bar moving dollars from one program to another, stripping much of the state flexibility that advocates were trying to create.
While the entire provision was rather low profile, it was one of the governors' favorites. And the Bush administration has been using it to counter complaints about the strict new work rules, which limit state options in working with welfare recipients.