The anti-corruption movement campaigned on a manifesto that included purging officials who broke rules cracking down on protesters, stopping party loyalists from leading public enterprises, and freeing the public broadcaster of political control.
Vučić and the SNS party have repeatedly denied corruption.
Vučić, who backs Serbia’s candidacy for the European Union while refusing to impose sanctions on Russia over its full-scale invasion of Ukraine, had pledged to increase pensions and public sector salaries, and investment in state healthcare.
Preliminary figures provided by Serbia’s election commission suggested a record high turnout, with 64.9% having cast their vote by 18:00 local time (17:00 GMT), two hours before polls were set to close.
Earlier in the day, long queues were seen outside polling stations in cities and towns across Serbia.
This was also the case outside booths in number of countries with sizeable Serbian communities – including Slovenia’s capital Ljubljana, Germany’s Munich, and Los Angeles and Chicago in the US.
In France, Serbian voters waited in line in heavy rain in Paris.
The election was held amid high tensions across Serbia, with police sealing off streets around the Republic Electoral Commission (RIK) in Belgrade.