Polls have suggested a win for his Progressive Party.
But discontent with Mr Vucic`s pro-EU stance looks set to bring ultra-nationalists back into parliament.
They oppose membership to the European bloc and favour closer ties with Russia.
These include Radical Party leader Vojislav Seselj, whose popularity has been boosted by his recent acquittal of crimes against humanity at the UN war crimes tribunal in The Hague.
This is Serbia`s third parliamentary election in under four years. Some 6.7 million people are eligible to vote.
Voting runs until 18:00 GMT and partial results are likely to come a few hours after that. There are no exit polls.
Opinion polls have indicated an absolute majority for Mr Vucic in parliament.
"We want to complete the process of privatisation, speed up (private) investments and above all to spur the entrepreneurial spirit of the people," Mr Vucic told Reuters news agency.
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