Sir Mark Thatcher is to be interviewed about his alleged role in a coup plot by Equatorial Guinea authorities.
Sir Mark Thatcher was released from house arrest after posting bail
He was arrested earlier this month by South African police accused of breaching South African laws and was released after posting bail.
The South African Justice Minister, Brigitte Mabandla, agreed to a request from Equatorial Guinea on Monday.
Sir Mark denies involvement in a coup to topple Equatorial Guinea's leader and is due back in court mid-November.
A South African Ministry of Justice spokesman confirmed that South Africa had agreed to the request.
The request will be forwarded to a Cape Town magistrate who will subpoena Sir Mark, son of former British prime minister Baroness Thatcher,
to testify about his alleged role in the conspiracy to topple President Teodoro Obiang Nguema.
A team of state prosecutors from Equatorial Guinea earlier arrived in South Africa and submitted a list of questions they want to put to the businessman.
A magistrate, appointed in Wynberg, Cape Town, will put the questions to Sir Mark under oath.
There is no time scale for this to happen, but it could take place this week.
Sir Mark is accused of helping to fund the purchase of a helicopter, breaching laws banning South African residents from taking part in foreign military action.
The 51-year-old, who denies any involvement in a coup, faces 15 years in jail if convicted.
He was under house arrest from 25 August until 3 September when he posted bail of £167,000, reportedly paid by his 78-year-old mother.
However, he cannot leave the Cape Peninsula and must contact police every day.