The new law will allow companies to strike individual deals with unions on working hours and overtime.
Since coming into office last year, President Nicolas Sarkozy has blamed the 35-hour week for damaging France's economic competitiveness.
Introduced 10 years ago by the then Socialist government, polls show most French still support the 35-hour week.
The new measures are expected to come into force at the end of August.
"Companies will at last be able to operate a management policy based on a secure legal framework, it's a remarkable advance for the economy," said Daniele Giazzi of the governing UMP party.
Having been approved earlier this month by the National Assembly - France's lower house of parliament - the measures passed a vote in the Senate - the upper house - late on Wednesday.
The bill was supported by the Senate's centre-right majority but opposed by the opposition Socialists.
The Senate also adopted other key measures reforming rules on strikes and unemployment benefits. Source