Long-time political rivals President Robert Mugabe and Prime Minister Morgan Tsvangirai said they cast identical 'Yes' votes in a one-day referendum on a new constitution that curbs presidential powers and is backed by all main political parties.
President Mugabe said he voted 'Yes' to the home-grown constitution to show how Zimbabwe mapped out its own future without outside interference.
"It gives us the right to determine together which way to govern ourselves," he said.
Mr Mugabe, 89, who led the nation to independence from Britain in 1980, has repeatedly accused Western governments of supporting efforts to oust him.
Mr Tsvangirai, thronged by supporters while voting at a junior high school south of Harare, said a 'Yes' vote marked a new turning point "and one of the most important historical steps" for the southern African nation after years of political and economic turmoil. He said it paved the way for a new chapter of the rule of law.
His supporters who have been killed in political violence over the past decade "will rest in peace because this is the most important stage we have been fighting for," Mr Tsvangirai said. "I hope everyone will exercise their vote as a preliminary step to free and fair elections."
Full scale presidential and parliamentary elections are pencilled in for around July to end a shaky and dispute-ridden coalition government formed by regional leaders after the last violent and disputed national polls in 2008.
There were no immediate reports of violence on Saturday after disturbances between rival youth groups on Friday. Mr Mugabe, voting at a school in western Harare, said he wanted peace to prevail.
Officials said polling was busy in populous districts after voting stations opened at 7am (0500 GMT) across the country. Small knots of voters turned out early in remote areas and less populated or wealthier suburbs.
The proposed constitution reduces the entrenched powers of Zimbabwe's president and includes a range of democratic reforms demanded by regional mediators in Zimbabwe's decade-long political and economic crisis.