With more than half the votes counted, conservative New Democracy took a commanding lead of 40.9 per cent, trouncing the radical progressive Syriza, which governed from 2015 to 2019, trailing with 20.1 per cent.
Analysts said New Democracy was likely to be short of a clear majority.
A newly introduced electoral system distributes seats based on how many parties get into the 300-member parliament, raising or lowering the bar for a majority accordingly to anything between 42 per cent and 47 per cent of the vote.
Greece's interior ministry projected that New Democracy could win 145 seats in parliament, six short of an absolute majority.
The result was however a boost to incumbent Prime Minister Kyriakos Mitsotakis, whose administration had to contend with a wiretapping scandal, the COVID-19 pandemic, a cost of living crisis and a deadly rail crash in February which triggered public outrage.
"It's a clear margin, a clear win," said Panos Koliastasis, adjunct assistant professor of politics at the University of Peloponnese.
Elections in Greece are held every four years for the 300-seat parliament.
A cost of living crisis dominated the campaign, with parties trying to woo voters with pledges to increase the minimum wage and create jobs.Â
A price surge has had a profound impact on Greeks, whose living standards had been eroded by a decade-long debt crisis.
Greece almost crashed out of the euro at the peak of its debt crisis in 2015.
Mitsotakis, elected in 2019, has portrayed himself as a safe pair of hands in his campaign to win the votes of about 10 million Greeks.
"Today the country's government responsibility has been passed on to you, the people, but I'm certain that tomorrow an even better day will dawn for our country," Mitsotakis told journalists earlier after casting his vote.
His administration, however, took the brunt of public outrage over a February 28 rail crash killing 57 people, and a wiretapping scandal targeting politicians.
