The agency cited concerns about its exposure to risky consumer lending.
(READ MORE: Capitec rides tough lending climate)
Moody's said in a statement it had cut Capitec's financial strength rating to D from D+, adding that all of the bank's ratings would be put on review for further downgrades.
(READ MORE: National credit regulator supports ABIL's curatorship)
Concerns about consumer lending in Africa's most developed economy have increased since the central bank launched a 1.6 billion US dollars rescue of African Bank Investments last week.