Mr Mnangagwa is set to land at 11:30am GMT, according to close ally Larry Mavhima.
Speaker of parliament Jacob Mudenda will hold a news conference at 08:30am GMT.
Mr Mnangagwa could be sworn in as the country’s next president today or tomorrow and is likely to lead Zanu-PF into elections next year.
Mnangagwa said: “I told the President that I would not return home now until I am satisfied with my personal security, because of the manner and treatment given to me upon being fired.”
The generals behind the military coup appeared to be trying to stop Mugabe’s wife Grace from succeeding the 93-year-old dictator when he dies and appear to favour Mnangagwa.
It has long been an open secret that the former state security chief hoped to succeed Mugabe.
The former vice-president was once a core member of Mugabe’s inner circle and helped direct the 1970s war of independence.
He served as Vice President of Zimbabwe from 2014 until earlier this month when he was dismissed “for plotting against the government”.
“What we’ve seen… is all about reasserting what the generals, and presumably Mnangagwa, see as the rightful succession to President Mugabe,” he added.
Born in central Zimbabwe in 1942, Mnangagwa grew up to become one of the richest men in Zimbabwe.
He studied for a law degree while in Zambia, before playing a key role in Zimbabwe’s bid for independence, which was granted in 1980.
After losing the Vice Presidency just over a week ago, Mnangagwa fled to South Africa.
Many believe that Mnangagwa and his ally General Constantino Chiwenga worked conspired together to have Mugabe and Grace removed.