"Be faithful to one partner and use a condom... Let us take precautionary measures. Give a child love, laughter and peace, not Aids," said Mr Mandela.
On the occasion of World Aids Day, Mr Mandela said the disease was threatening the very fabric of South African society.
The issue is particularly sensitive in South Africa as Mr Mandela's successor, Thabo Mbeki, has questioned the link between HIV and Aids.
South Africa has one of the world's highest rates of Aids infection with at least 10% of the population - about 4.5 million people - already carrying HIV.
Coinciding with World Aids Day, US pharmaceutical company Pfizer was announcing its plans to provide the South African Government with a free two-year supply of its Aids medication, Diflucan.
'Invisible enemy'
In his World Aids Day message, Mr Mandela said: "Our country is facing a disaster of immeasurable proportions from HIV/Aids.
"We are facing a silent and invisible enemy that is threatening the very fabric of our society.
"Be faithful to one partner and use a condom... Let us take precautionary measures. Give a child love, laughter and peace, not Aids," said Mr Mandela.
The former president stressed the need to destigmatise the disease and encourage people to talk about it.
"Leaders in all spheres who are living with HIV should be encouraged, not coerced, to lead by example and disclose their HIV status," Mr Mandela said.
Medicines
Pfizer said on Friday that it had signed a deal with the South African Government to supply its drug Diflucan free of charge for a two-year period.
Diflucan treats a type of meningitis of the brain as well as a form of meningitis of the oesophagus, which affects up to 40% of Aids patients.
The announcement follows a recent United Nations report which found that the number of those affected by Aids or the HIV virus in the sub-Saharan Africa now totals 25.3 million. The figures represent an increase of 17.7% from a year ago.
Worldwide, more than 30 million people are thought to have HIV.
The Pfizer initiative has been received with scepticism by some activists who maintain that the international focus should be getting as many people treated cheaply, efficiently and safely rather than on a particular drug for one or two indications.