Labour and Employment minister had been in self-quarantine at his home.
South Africa's Labour and Employment minister Thulas Nxesi, 61, became the second high profile government official to be hospitalised for Covid-19 in under 24 hours.
His Cabinet colleague Gwede Mantashe, who heads the Mineral Resources portfolio, was on Monday admitted to hospital.
Nxesi became the fifth MP to test positive for the coronavirus, last week on Friday and had been in self-quarantine at his home.
Cabinet spokesperson Phumla Williams on Tuesday said Mr Nxesi's admission to hospital was on the advice of his doctors.
"His admission to hospital on Monday night comes on the advice of his medical doctors for him to have access to better medical attention and proper monitoring," Ms Williams said.
On Monday, Cedric Frolick, the National Assembly chairperson responsible for committees, oversight and information and communications technology, also tested positive for Covid-19.
Frolick is self-isolating, according to speaker Thandi Modise. National Council of Provinces chairperson Amos Masondo wished Frolick a speedy recovery.
Three provincial premiers have also contracted the coronavirus.