A total of 498,305 voters are eligible to cast their ballots in polling stations which opened at 8:00 local time (0600 GMT) and would last until 21:00 (1900 GMT).
The first unofficial results will be known shortly after polling closes, while official early results are expected by midnight.
Opinion polls have indicated that the European Montenegro coalition led by Prime Minister Milo Djukanovic's long-time ruling Democratic Party of Socialists (DPS) was expected to secure more than 50 percent of the vote.
The European Montenegro coalition also includes the Social Democratic Party (SDP), a long-time DPS ally, and two parties of ethnic minorities -- the Croatian Civil Initiative and the Bosniak Party.
Djukanovic, 47, who has ruled Montenegro with the DPS since 1991, was most likely to retain his premiership.
