President George W. Bush has promised to veto the measure, which would add $35 billion to the program, generally referred to as S-CHIP, during the next five years.
The bill passed the Senate by 67 to 29, enough to override a veto, The Washington Post reported. A number of Republicans crossed party lines to vote with the Democratic majority.
The House approved the legislation Tuesday, but by a smaller margin, 265 to 159.
Much of the Republican support Thursday came from legislators who face strong re-election challenges next year. Even some conservatives, like Sen. Pat Roberts, R-Kansas., jumped ship and asked Bush to reconsider his veto threat.
"Anyone who votes in lock step with the president and against children's health, they are going to hear about it back home," said Rep. Chris Van Hollen, D-Md., chairman of his party’s congressional campaign committee.