Elections Ontario says the number of voters casting an advance ballot has dropped significantly compared with the 2011 race.
Advance polls for this year's election were open for a week ending Friday, and in that time, 566,845 people cast a ballot.
That's down roughly nine per cent from the last election, when 624,958 people voted in advance.
Opinion polls have consistently shown a high number of undecided voters ahead of Thursday's election.
The last election saw the lowest turnout in the province's history, with only 49 per cent of voters casting a ballot.