Africa's biggest bank by assets, along with all of South Africa's major lenders, had already warned that profits would likely be at least 20% lower, with the pandemic prompting a spike in bad loans and also hitting new business and fee income from transactions.
Its headline earnings per share - the main profit measure in South Africa - for the six months to June 30 would likely fall by between 30% and 50%, compared to the 837.4 cents it reported in the same period last year, it said in a trading update.
"The group remained well capitalised and liquid," it continued.
South African lenders, which managed to shield themselves from the more devastating impact of the 2008-2009 financial crisis, are now facing one of their biggest ever hits to profits as a result of the pandemic.
South Africa's economy, already in recession, is forecast to decline by over 7% this year, according to the central bank, and the Banking Association of South Africa has warned problem loans could rise to their highest ever level of 10%.
Standard Bank did however say it is set to benefit from a bigger than expected gain on the sale of its 20% stake in ICBC Argentina to the Industrial and Commercial Bank of China, thanks to the slump in South Africa's rand.
The group will now get 1.4 billion rand ($85.06 million) as a result, rather than 600 million rand.
($1 = 16.4591 rand)
(Reporting by Emma Rumney; Editing by Olivia Kumwenda-Mtambo, Kenneth Maxwell and Louise Heavens)