President Cyril Ramaphosa is expected to announce changes to the National Executive at the Union Buildings, Pretoria, at 15:00 on Thursday.
In a statement issued on Thursday morning the Presidency said "these changes have been occasioned by the passing away in September 2018 of the Minister of Environmental Affairs, Ms Edna Molewa, and the more recent resignation of the Minister of Home Affairs, Mr Malusi Gigaba".
Gigaba resigned as a Cabinet minister on November 13 amid a series of reputational knocks to his public image, ranging from a leaked sex tape and being found to have breached the executive ethics code by lying under oath.
"I did so after a long period of sustained and vitriolic public attacks on my integrity. I wish to state that my resignation is not an admission of guilt on my part," Gigaba said in a statement on the day he resigned.
He said that the integrity of government and the ANC were more important than him being in political office. He resigned as an MP a few days later.
Following Gigaba's resignation Transport Minister Blade Nzimande took over as the acting home affairs minister.
Molewa died on September 22. Her family said in a statement that she died from Legionnaires' disease - an extremely acute form of pneumonia. She was 61 years old.
"Our sister passed away yesterday, 22 September 2018 following complications of Legionnaires' disease," said the minister's brother Fana Mmethi in a statement issued on behalf of her family.
Earlier this year, Ramaphosa announced significant changes to his cabinet in February this year, after he took over the position of President from Jacob Zuma.