The Centre Party, which has ties to Russian president Vladimir Putin, is expected to do well.
However, the Centre Party is seen as a pariah by other parties, who are likely to band together to renew the current governing coalition.
Estonia was once part of the former Soviet Union but is now a NATO member.
PM Taavi Roivas has voiced concerns that Russia could seek to destabilize other former Soviet states.
He has called for an “Estonian-minded government”.
At 35, Taavi Roivas is the youngest prime minister in Europe.
Estonia has seen a number of airspace violations by Russia, and last year a security official was detained by Russia and accused of spying.
The Centre Party leader, Edgar Saavisar, favours a friendlier approach to Moscow, and has suggested that Russia’s annexation of Crimea could be legitimate.
About a quarter of Estonia’s 1.3 million population are ethnic Russians, many of whom are Centre Party supporters.
Estonia is a pioneer of electronic voting, with a reported one in five casting their vote online.
Voting is due to end at 20:00 local time.
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