The first agreement was narrowly rejected in a referendum last month.
President Juan Manuel Santos says the new proposals are stronger and take into account the changes demanded by opponents of the scheme.
Those opponents, led by former President Alvaro Uribe, say the revised deal is still too lenient on Farc leaders.
The revised agreement now goes to the lower house of Congress for approval.
The peace accord is aimed at ending an armed conflict that has killed more than 260,000 people over five decades.
The two sides reached an agreement earlier this year after four years of talks in the Cuban capital, Havana.
Before beginning their session, senators held a minute's silence for those who died in a plane crash near the city of Medellin on Monday.
BBC News |