A statement says the 94-year-old anti-apartheid icon is "receiving appropriate treatment and he is responding to the treatment."
Mandela was hospitalized Saturday at 1 Military Hospital near South Africa's capital, Pretoria.
In January 2011, Mandela was admitted to a Johannesburg hospital for what officials initially described as tests but what turned out to be an acute respiratory infection.
Mandela is revered for being a leader of the struggle against racist white rule in South Africa and for preaching reconciliation once he emerged from prison in 1990 after 27 years behind bars. He served one five-year term as president before retiring from public life.