The North African country is under pressure from the International Monetary Fund (IMF) to speed up reforms and help its economy recover from militant attacks in 2015 that hurt its vital tourism industry.
The new law raises the retirement age for civil servants from 60 to 62 as of 2020. It also imposes a 1 percent social security tax on employees and a 2 percent tax on employers.
Tunisia's state social security funds suffer from a deficit of about $1 billion, as the economy has been in turmoil since the 2011 uprising against autocrat Zine El-Abidine Ben Ali, according to officials.
The country has been praised for its democratic progress since 2011 but successive governments have failed to push through potentially painful reforms to trim deficits and create growth.
Under the 2019 budget, the budget deficit will narrow to 3.9 percent of gross domestic product in 2019, from about 5 percent in 2018.