Exit polls suggest that the party of Japanese Prime Minister Shinzo Abe has secured a large majority in the country's parliamentary elections.
Abe had called a snap poll to boost support for his economic reforms.
He was elected in 2012 and has tried to revive the economy by raising public spending and printing money.
After an initial burst of growth, Japan slipped back into recession in the second half of this year.
Despite exit polls showing Abe's conservative Liberal Democratic Party ahead, analysts said it would probably fall short of a two-thirds majority - meaning it was likely to remain in coalition with junior partner Komeito.
Reports said turnout at polling stations was low due to voter apathy and heavy snowfall. Preliminary results are expected at midnight local time (15:00 GMT).
Japan is the third-largest economy in the world, according to the World Bank, but it has struggled in recent years.
Abe has insisted that his policies, known as "Abenomics", can get Japan back on track.
"I promise to make Japan a country that can shine again at the centre of the world," he said in a recent campaign speech.
Among his pledges, Abe vowed to help more Japanese women enter and remain in employment by tightening anti-discrimination laws and setting employment targets.
He has also promised to amend the law to allow the Japanese military to engage in collective self-defence alongside allies who are threatened.
Economists say an increase in sales tax from 5% to 8% in April knocked consumer spending and helped to halt growth.
The tax increase was legislated by the previous government in 2012 to curb Japan's huge public debt, which is the highest among developed nations.