The election has been overshadowed by tension over Russia's growing support for the Georgian separatist Abkhazia province.
Saakashvili's party faces 11 other political forces in the election for the parliament's 150 seats, half of which will be filled by nationwide voting for parties and half by voting for individual candidates.
The main United Opposition Council and up to three other opposition parties are expected to clear the five per cent hurdle needed to win seats.
Nearly 3.5 million Georgians are eligible to vote.
Russia has sent thousands of soldiers to Abkhazia in apparent support of the region's political aspirations.
However, since Saakashvili's opponents share both his wariness of Russia and his pro-Western views, the issue is more a platform for scoring points than for major policy debate.
Saakashvili, a US-educated lawyer, is a staunch ally of George Bush, the US president, having committed Georgian troops in Iraq.
He was initially elected by a landslide after leading the Rose Revolution protests that ousted his predecessor in 2003.
However, accusations of authoritarianism and his failure to lift the country out of hardship despite economic growth have dented his popularity.
His crackdown last November, when police used tear gas and water cannon against protesters demanding his resignation, angered many Georgians and alarmed Western governments.
He was re-elected by a far slimmer margin in January, but the opposition alleged widespread fraud and the West urged Georgia to improve democratic practices.
When Nato declined to grant Georgia a road map for membership last month, it stressed that members looked forward to "free and fair parliamentary elections" and scheduled a review of the issue for December.
Georgia has enacted electoral reforms since the presidential vote in a bid to meet these demands and appease the opposition.
|Tension over Russia's support for Abkhazia |
has overshadowed the election [AFP]
Saakashvili has promised honest elections and has sternly warned officials against illegal practices.
But preparations for the vote have received mixed reviews.
In an interim report earlier this month, the Organisation for Security and Co-operation in Europe's vote monitoring body said "several allegations of intimidation" had been substantiated.
Saakashvili's opponents have alleged campaign violations and warned against fraud in the vote count.
Speaking to a crowd of thousands on Sunday, Levan Gachechiladze, leader of the United Opposition Council, urged supporters to gather after polls close to hear the "real results of the voting'.'
Merab Pachulia, a Georgian political analyst, said: "If the authorities falsify the results, there will be an explosion."