Speaking on the sidelines of a conference aimed at courting South African investors, Mnangagwa noted that the last election in 2013 "was free of any violent incidents."
"We believe that we shall have a free and a fair election during 2018," he told reporters, pledging that the upcoming presidential and parliamentary ballot would, like the last, be "free of violence."
Previous elections have been marred by violence against opponents of President Robert Mugabe as well as voter intimidation and alleged fraud.
Opposition leader Morgan Tsvangirai believes Mugabe's party has never fairly won any election in recent times.
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"ZANU-PF has not won recent elections, it has rigged them," he told AFP last month, saying he didn't expect Mugabe to come out and commit to "create conditions for free and fair elections."
Mnangagwa said political parties had agreed to electoral reforms to "level the playing field" including the creation of voter registers based on polling stations rather than constituency-based rolls.
Previous ballots have been marred by allegations of the exi'tence of ghost voters, with names listed of people who were long dead, were under age or who never even existed.
Opposition parties are trying to forge an electoral alliance in a bid to oust the 93-year-old Mugabe whom the ruling party is fielding.
But Mugabe has scoffed at the planned alliance as combination of zeros saying it would make victory easier for his ruling party as it focusses on one common rival rather than separate opponents.