When polls opened at 7:00 am (1130 IST), dozens of voters were already queueing outside one polling station in Marseille Street in central Tunis, an AFP correspondent reported.
The North African nation has been hailed as a beacon of hope compared with other chaos-hit countries like Libya and Egypt where regimes were also toppled.
But its transition has been tested at times by militant attacks and social unrest.
Prime Minister Mehdi Jomaa hailed today's vote as "historic".
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Jomaa had warned of possible jihadist attacks aimed at disrupting the country's first post-revolution parliamentary election.
On Friday, Tunisian police killed six suspected militants -- five of whom were women -- in a raid on a house in the outskirts of the capital.
A policeman was also killed in an earlier firefight with the suspects.
Up to 80,000 troops and police have been deployed in a bid to protect voters.
The revolt ousted veteran autocrat Zine El Abidine Ben Ali and ushered in a coalition government and interim president that won praise from the international community.
Several parties competing for seats in parliament are fronted by former regime officials.
Although they have publicly sought to distance themselves from the repression and intimidation practised under the ex-president, many voters who took part in the revolution are angered at the prospect of Ben Ali associates returning to parliament.
"These politicians aren't worth a minute of my time. They are incompetent and have impoverished the people," said street vendor Bechir Bejaoui.
Five million Tunisians are eligible to vote in a closely monitored election that interim president Moncef Marzouki has dubbed a "defining moment".
Voters could be seen exiting polling stations with index fingers dyed in ink -- a measure designed to prevent people casting multiple ballots -- held up in celebration.