President Barack Obama is hoping for quick approval so that the point man for the administration's economic rescue effort can begin work.
The committee vote came a day after Geithner appeared before the panel to apologize for what he called "careless mistakes" in failing to pay $34,000 in taxes earlier in the decade, when he worked at the International Monetary Fund.
Geithner paid the back taxes plus interest for the years 2003 and 2004 after being audited by the Internal Revenue Service. But he did not pay taxes he owed for 2001 and 2002, even though he had made the same mistakes for those years, until shortly before he was nominated by Obama last November to be treasury secretary.
The nomination was expected to win approval by the full Senate, with many lawmakers saying that given the serious economic crisis facing the country, the new president deserved to have the services of a man of Geithner's abilities and experience.
Geithner has been the head of the Federal Reserve Bank of New York for the past six years and was a key participant in decisions made by the Bush administration to deal with the worst financial crisis to hit the country since the Great Depression.
All five of the "no" votes on the committee came from Republicans, including the top GOP member of the panel, Sen. Charles Grassley, R-Iowa. Those voting no said that they did not believe Geithner had been candid in his answers on why he failed to pay Social Security and Medicare taxes. They said they viewed this as a serious error for an official who would head the agency that oversees the IRS.
"I am disappointed that we are even voting on this," said Sen. Michael Enzi, R-Wyo. "In previous years, nominees who made less serious errors in their taxes than this nominee have been forced to withdraw."
Even Democrats who voted for the nomination said they were disappointed in Geithner's actions.
Sen. Kent Conrad, D-N.D., said that in normal times he would oppose Geithner but "these are not normal times."
The committee acted on an expedited basis, voting shortly after Geithner submitted to the panel 102 pages of answers to written questions committee members had posed after Wednesday's hearing.
In response to one of those questions, Geithner pledged that the Obama administration would carry out reforms in the $700 billion financial rescue program. The Bush administration was widely criticized for distributing the first $350 billion from the fund with not enough attention paid to ensuring that banks receiving the money would use it to increase lending. Former Treasury Secretary Henry Paulson had earmarked $250 billion of the first $350 billion to go to purchasing stock in banks as a way of bolstering their balance sheets.
In answer to one of the committee's questions, Geithner said the new administration planned to require that banks receiving government support "provide detailed and timely information on their lending patterns, broken down by category." Geithner said that public companies will be required to report this information on a quarterly basis.
Last week, the Senate rejected an effort to block release of the second $350 billion from the rescue fund.
During his testimony on Wednesday, Geithner said the new administration would release a comprehensive plan within a few weeks providing details on how it planned to combat the financial crisis and current recession, which is already the longest in a quarter century.
Geithner did not go into detail on what might be in that program but he acknowledged that the administration is considering buying toxic assets now weighing on the balance sheets of many banks.
In addition to deploying the second half of the $700 billion bailout fund, the administration is pushing Congress to quickly pass an $825 billion-plus economic stimulus program of tax cuts and increased government spending to jump-start the economy.