No updates were given on his condition on Sunday. The president’s office said earlier there was no indication that there was any reason for alarm.
The former leader spent 18 days in hospital in December.
He was treated for a lung infection and gallstones. His health has been a cause of concern for many years.
A message posted by President Jacob Zuma’s office on Saturday said Mr Mandela had been admitted for a check-up at a Pretoria hospital on Saturday afternoon.
It said the aim was “to manage existing conditions in line with his age”.
Mr Mandela served as South Africa’s first black president from 1994 to 1999 and is widely regarded as the father of the nation for leading the struggle against apartheid and for democracy.
He first contracted tuberculosis in the 1980s while detained in Robben Island prison.
He has been admitted to hospital on three occasions in the past two years. In January 2011, he was treated for a chest infection in Johannesburg.
During his latest stay in hospital, President Zuma at one point described his condition as “serious”, but added that he was responding to treatment.
The former president has been rarely seen in public since retiring from public life in 2004.