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.
READ: Gigaba falls on his sword and resigns from cabinet
Following Gigaba's resignation Transport Minister Blade Nzimande took over as the acting home affairs minister.
Molewa died on September 22. She reportedly fell ill while on a state visit to China hosted by President Xi Jinping in Bejing at the beginning of September.
Her family said she died from Legionnaires' disease - an extremely acute form of pneumonia. She was 61 years old.
READ: From teacher to minister: Molewa's life was one of service
"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.
February cabinet changes
Earlier this year, Ramaphosa announced significant changes to his cabinet in February, after he took over the position of President from Jacob Zuma.
At the time, Ramaphosa described his cabinet as a "transitional one".
"No, no, this is a transitional Cabinet. It is the Cabinet that will take us to the next elections," Ramaphosa told eNCA's Annika Larsen.
Ramaphosa said the leadership of the ANC was still coming up with proposals for the reconfiguration of a new Cabinet.