The vote passed 257-41, following passage in the lower Chamber of Deputies last week.
Mr Monti said the package was “of extreme urgency and will allow Italy to face the European crisis with its head held high.”
Among the disputed measures is a reform to Italy’s generous pension system, which will require Italians to work longer.
Many of Silvio Berlusconi’s loyalists, who make up parliament’s largest party, also opposed the decision to revive a home property tax that the former prime minister had eliminated.
Unions staged strikes and demonstrations last week to protest against the measures.
Mr Monti has said the tax hikes, reforms and other measures was the only way to save Italy financially and give young Italians a foundation for economic recovery and growth.