The tourists boarded a bus to take them to their hotel on Sunday evening, but they were apparently followed by armed criminals monitoring the terminal.
The bus was pulled off the road by a fake police car, and at least one robber was wearing a police uniform.
"The men allegedly demanded their possessions and one of the tourists was injured and taken to hospital," police said in a statement.
"Most of the passengers are 70-plus. People panicked and even got firearms aimed at them. In two cases' the trigger was pulled but the gun didn't fire," South African media quoted one tourist as saying.
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The bus driver and the tour guide were tied up as the robbers ransacked luggage, Dutch media reported.
"We are safe now. But we are in shock and want to go back. We just landed for a 22-day trip, but the fun has gone," another traveller said.
Authorities say that tourists are seldom targeted, but airport travellers have previously been the victims of criminals following vehicles from Johannesburg's OR Tambo airport.
"More has been done... in preventing and combatting criminal activities at the airport," said police minister Fikile Mbalula, who was due to visit the victims later today.