"They were having supper when a number of men with guns entered the house, tied them up, assaulted them and demanded money," national police crime intelligence spokesman Tumi Golding said.
The incident took place on Friday night in the posh Bryanston quarter in the north of the city.
The unnamed minister was visiting a family friend when the robbers came and made off with jewellery, money and electronic goods.
Golding said she could not reveal the identity of the minister or why he was in the country as she was waiting for clearance from Zimbabwean authorities.
South Africa has one of the world’s highest crime rates and is struggling to clean up its record before hosting the Football World Cup next year
Meanwhile, a second body of a Zimbabwean was found in an illegally occupied building which caught fire in Johannesburg, emergency services said on Saturday.
Spokesman Percy Morokane said a second body was found on Saturday morning at the building next to the New Doornfontein train station.
"This was a very difficult operation, the team had to come with heavy equipment to locate the body," said Morokane of the search and rescue operation.
Both bodies found were male aged 31 and 32, it is also alleged that they were Zimbabwean nationals.
Morokane said a couple were allegedly fighting in the building and a candle was knocked over during their argument.
This may have caused the fire.
"We will investigate all possible cases, nobody was injured except for minor cases of smoke inhalation," he said.
Morokane said fire fighters rushed to the block of flats on Buxton street after they were informed of the fire at 11.45pm on Friday.
"The first floor caved in but 20 fire fighters managed to contain the fire after an hour and a half ," said Morokane.
The first body was found in a heap of rubble but could not be removed because the search and rescue team felt it was unsafe to do anything inside the building, he said.
About a 100 illegal occupants, including children, managed to run out of the building before the first floor collapsed.
Morokane said disaster management was arranging blankets and "if possible", food parcels for those left sleeping outside.
The disaster management policy states that people occupying illegal buildings do not qualify for relief.
However, he said they will give them "humanitarian aid on humanitarian grounds".
The building was closed down last year for safety reasons.
"Police sniff dogs are on the scene to make sure that no other bodies are left behind," said Morokane