However they denied US President George W Bush the indefinite extension he was seeking.
The compromise deal was reached after a marathon closed-door negotiating session, and extends provisions of the act for just six months, despite massive pressure from Mr Bush and other top administration officials.
"The work of Congress on the Patriot Act is not finished," said Mr Bush in a statement after the Senate approval.
"I look forward to continuing to work with Congress to re-authorise the Patriot Act."
Mr Bush, who had previously said he would veto a three-month extension, appeared happy with the compromise, saying that he is pleased "that existing law remains in place."
As part of the accord, opponents of the act in its current form - who come from both political sides - agreed to abandon their filibuster of the act and the Republican majority dropped its opposition to a temporary solution.
Republican leaders tried to break the filibuster - a tactic of extending debate to delay a vote - but could only muster 52 of the needed 60 votes, with four Republicans crossing the floor to oppose the extension.
On the same day, the New York Times reported that Mr Bush authorised eavesdropping on citizens without a warrant.
Bipartisan support
Both sides appear content with the compromise six-month extension.
"This is a commonsense solution that gives the Senate more time to craft a consensus bill that will promote our security while preserving our freedom," said Patrick Leahy, the top Democrat on the Senate Judiciary Committee, in a statement.
Senator Leahy, who led the drive against extending key provisions of the act in their current form, said he is pleased that the Republican leadership "listened to a bipartisan majority of us in the Senate" on this matter.
Democratic Senate Minority Leader Harry Reid said the compromise gives Congress the necessary time to once again examine the US Patriot Act and to amend it so that "it allows us to fight the terrorists and protect the Constitution".
Republican Majority Leader Bill Frist, who had been one of the most outspoken supporters of re-authorising the provision, said the agreement is evidence that "there is broad bipartisan support that the Patriot Act never should expire".
A few days ago he had brushed off any thought of temporary solutions.
"This is a win for America's safety and security, and I'm pleased the Senate was able to rise above the partisan politics being played by the minority to do the right thing," he said in a statement.
"We should build on this effort to strengthen these anti-terrorism tools, safeguard our civil liberties and permanently extend the remaining provisions."
At least one Democrat said he approved the Republican concessions.
Senate Minority Leader Harry Reid said Congress now has time to get the Patriot Act right, saying the extension strikes a balance between security and privacy concerns.
The act, which was enacted barely six weeks after the September 11 attacks in 2001, is seen by the Bush administration as a key legal tool in the war on terrorism.
It gives the federal government greater search and surveillance powers by streamlining procedures and eliminating red tape.
Investigators can obtain warrants to intercept telephone conversations conducted by a terrorism suspect or monitor email traffic from any computer.
The law also makes it possible for the US government to obtain banking, medical or library records.
But mindful of concerns the act could make Americans more vulnerable to government intrusion, Congress had equipped 16 of its key provisions with "sunset" features, making sure that, unless renewed, they will automatically expire at the end of this year.
Two of these deal with the government's access to library records and roving telephone taps, something civil libertarians say is excessively invasive.
The future of the Patriot Act was further called into question following revelations last week that the president had repeatedly authorise electronic wiretaps inside the United States without a requisite court order, a decision that some said was a violation of US law.
The act is due to expire at midnight on December 31.
The House of Representatives is expected to take up the compromise on Thursday.