Amid tightly fought election and high turnout, the Zanu-PF leader Mugabe is running for office for the seventh and perhaps final time.
The 89-year-old Africa's oldest leader, accompanied by First Lady, Grace, voted before lunchtime at Mhofu Primary School in Highfield in Harare, where he insisted the poll would reflect the will of the people.
"I am sure people will vote freely and fairly, there is no pressure being exerted on anyone," he said.
"Why do I offer myself as a candidate if it is to cheat the people by resigning soon after," he added.
He also said that if re-elected, he would work hard to fix the economy and revive industries.
Mugabe's allies wish to extend his 33-year rule, who has held this position since 1980.
On Tuesday, Mugabe vowed to step down if his rival Morgan Tsvangirai was the victor.
Tsvangirai, the current prime minister, said that promise should be taken "with a pinch of salt".
At many stations voters started queueing before sunrise in the winter cold hours before polls opened. The lines continued well into the evening, with many marking their ballots by candle light.
The Zimbabwe Electoral Commission has said that the presidential and parliamentary election results will be announced by August 5.
(With Agency inputs)