It has been more than two months after hospital doctors treating him for a lung infection let him return home to recover, the South African government said on Monday.
The former South African president was still "quite ill" and unable speak because of tubes in his mouth to clear fluid from his lungs, ex-wife, Winnie Madikizela-Mandela, told the Sunday Independent newspaper.
"The bedroom there is like an ICU ward," the newspaper quoted her as saying.
The anti-apartheid leader spent 87 days in a Pretoria hospital before returning to his Johannesburg family home in September.
He was receiving round-the-clock treatment from 22 doctors and used facial gestures to communicate, Madikizela-Mandela told the newspaper. Medics were hopeful he would recover his voice, she added.
The 95-year-old made his last public appearance waving to fans from the back of a golf cart before the Fifa Soccer World Cup final in Johannesburg in 2010.
In April state broadcaster aired a clip of the thin and frail statesman being visited by President Jacob Zuma and top officials from the African National Congress.
Mandela was elected South Africa's first black president in multi-racial elections in 1994 that ended white minority rule. His imprisonment included 18 years on the notorious Robben Island penal colony, when he and other prisoners were forced to work in a limestone quarry and he first suffered the lung infections that were to dog him for years.
"The health of the former President remains much the same ... Which is stable but critical" the government said in a statement. He continued to respond to treatment, it added.