The African National Congress MP and her daughter Zindzi arrived at the Medi-Clinic Heart Hospital after midday in a black Audi fitted with blue police lights.
Photographers rushed into the busy Park Street to take photos of the pair.
Earlier, Mandela's granddaughter Tukwini was spotted at the hospital. She was with three other relatives.
Security at the facility remained tight, with several police officers searching all vehicles entering the hospital's two entrances.
A media scrum of local and international reporters and broadcasters has been stationed outside the hospital since Mandela was admitted on Saturday.
Mandela was hospitalised in the early hours of Saturday morning with a recurring lung infection. The presidency said he was in a "serious but stable" condition.
President Jacob Zuma, accompanied by African National Congress treasurer general Zweli Mkhize, visited the ailing icon on Thursday.
"Madiba's health continues to improve but his condition remains serious," Zuma said in a statement.