There are no opinion polls, but the moderate Islamist Ennahda party is predicted to do well.
Turnout reached 65% an hour before the close of voting, state TV reported.
A series of democratic changes have taken place since the authoritarian leader Zine al-Abidine Ben Ali was ousted in 2011.
Tunisia is seen as the birthplace of the Arab Spring - the pro-democracy movement which sought to replace autocratic governments in several Arab countries.
Tunisia is considered to have had the most successful outcome, with relatively low levels of violence.
At the scene: Naveena Kottoor, Tunis
Despite a rainy and damp start to the day, there were queues outside this polling station in the Tunis 2 district, with some carrying the Tunisian flag.
In this district, voters have a choice between 45 candidates. The entire process is being tightly observed by around 800 international, as well as more than 10,000 national, election monitors across the country.
The security presence is visible at the polling stations and on the streets.
Today marks the end of the political transition period from dictatorship to democracy. It's a milestone, the expectations are high, not just in Tunisia but abroad as well.
Ennahda's main rival is likely to be the liberal Nidaa Tounes (Tunisia's Call), although it has promised to seek a coalition government even if it wins the most seats.
Most of the major parties have vowed to tackle Tunisia's high unemployment and to reinvigorate its economy.
Polls opened at 07:00 (06:00 GMT) and closed at 18:00 (17:00 GMT). Results are expected on Wednesday.
More than 50,000 security personnel and nearly 20,000 soldiers were ordered to be deployed on Sunday to ensure safe voting.
Radical groups within Tunisia have threatened to disrupt the elections and on Thursday militants shot a policeman on the outskirts of the capital, Tunis.
Casting his vote on Sunday, Prime Minister Mehdi Jomaa said "the whole world is watching Tunisia today".
Earlier Mr Jomaa warned that extremist groups could attempt to attack polling stations.
"We know that this [election] will be a target because it is unique in the region. It brings hope," he said, during an inspection of troops near Tunis.
Around five million Tunisians were registered to vote, with overseas residents having already cast their ballots on Friday.
Ennahda, which currently rules in coalition with other parties, has promised to pursue a unity government even if it wins the most seats.
Tunisia is set to hold a presidential election on 23 November, which will deliver the country's first directly elected leader since the removal of Ben Ali in 2011.
Protests which began in the Tunisian town of Sidi Bouzid in late 2010 later gathered pace and spread across much of the Arab world the following year.
Tunisia has voted in elections to its first parliament under a new constitution, part of political changes under way since the "Arab Spring".