Results were expected within hours.
The opposition held just two seats in the 84-member parliament dissolved in April but the ruling People's Action Party (PAP) admitted during the campaign that many voters were unhappy over issues like the rising cost of living and immigration policies.
The Straits Times newspaper reported on its web edition that 83 percent of the record 2.21 million voters had cast ballots by 5:00 pm (0900 GMT), three hours before polling stations closed.
The turnout in 2006, when there were only 1.22 million voters, was 94 percent.
As a result of compulsory voting, turnout in Singapore elections has traditionally been higher than 90 percent, according to a tally by the Swedish-based International Institute for Democracy and Electoral Assistance.