The MPs are Lerato Theko, Terence Mpaza, Simanga Mbuyana, Joseph Office, Rachel Adams and Theophilus Nkozo, Parliament said.
Former transport minister Dipuo Peters, former energy minister Tina Joemat-Pettersson, former public service and administration minister Ngoako Ramatlhodi, former deputy finance minister Mcebisi Jonas and former deputy arts minister Joyce Mabudafhasi stepped down as MPs after having their portfolios taken away.
There had also been a long-standing vacancy in the ANC benches.
The former ministers who quit were criticised for doing so by ANC secretary-general Gwede Mantashe.
He accused them of resigning to hold onto their ministerial pension benefits, but it is believed that some left to escape the party sanction they would almost certainly incur if they broke ranks and voted in favour of a motion of no confidence in President Jacob Zuma that has been tabled by the opposition. - ANA