Cape Town - President Cyril Ramaphosa will announce changes to the National Executive at the Union Buildings at 3 pm on Thursday, the Presidency said.
"These changes have been occasioned by the passing away in September 2018 of the Minister of Environmental Affairs, Edna Molewa, and the more recent resignation of the Minister of Home Affairs, Malusi Gigaba," a statement said.
This will be Ramaphosa's first change to the Cabinet which was sworn in in February.
Molewa, 61, died in September after a short illness.
Gigaba resigned as Home Affairs Minister earlier this month after a string of scandals, including the legal action between himself and the Oppenheimers over the VVIP terminal.
The Gauteng High Court ruled that Gigaba had lied under oath over the matter.
The minister was dealt a blow when the Constitutional Court dismissed his application to appeal the high court ruling. The court said the case was unlikely to succeed.
This was the second blow for Gigaba after Public Protector Busisiwe Mkhwebane found that Gigaba violated the constitution and the executive ethics code when he told untruths under oath in court.
A video of Gigaba performing a sexual act on himself - which he says was stolen when his phone was hacked - was also been widely circulated on social media, drawing strong criticism from opposition parties.
According to the Presidency, Gigaba indicated in his letter of resignation that he was stepping aside "for the sake of our country and the movement to which he belongs".
Minister of Transport Dr Blade Nzimande has been acting as Minister of Home Affairs.
Since taking office in February, Ramaphosa has only effected one Cabinet change, appointing Tito Mboweni as finance minister following the resignation of Nhlanhla Nene.
Media reports this week have suggested the president would combine several portfolios in the economics cluster to create a "super-ministry" to spearhead efforts to revive growth and attract investment.