"We are here … just to see how things are before the actual election day," Nkosazana Dlamini-Zuma said on arrival.
But the South African's visit comes amid questions about the fairness of the vote and about the status of the African Union's (AU) observer mission.
With a week to go before the July 31 poll, the head of the AU observer mission, Nigeria's former president Olusegun Obasanjo, has not yet arrived in the country.
"I think he will come if he is allowed," said Dlamini-Zuma without elaborating.
In the early 2000s Obasanjo led a Commonwealth delegation to Zimbabwe that tried to mediate the end to a crisis sparked by the seizure of white-owned farms and a crackdown on the opposition.
AU observer mission spokesperson Hajra Omarjee said that Obasanjo "is arriving later this week".
Members of the roughly 60-strong AU observers team have been deploying in batches.
The first group arrived last month.
About 600 foreign election observers, mainly from African bodies, have been accredited to observe the polls, while 6 000 local observers will also be watching the vote.
Zimbabwe did not invite Western observer missions because of sanctions imposed on President Robert Mugabe and his top officials for rights abuses.
Concerns have arisen about the chaotic state of Zimbabwe's voter roll, fuelling fears of fraud and irregularities.
The election will end an uncomfortable power-sharing government formed by Mugabe and Prime Minister Morgan Tsvangirai after violent and disputed polls in 2008.
The 89-year-old Mugabe, who is vying to prolong his 33-year-rule, will be running for the seventh time. – AFP