Telkom, which still without a chief financial officer, said Moholi would begin work from the beginning of April.
Moholi, the current managing director of Telkom's domestic unit, has spent a total of 12 years at the company, whose biggest shareholder is the South African government.
She would take over from acting CEO Jeffrey Hedberg, whose contract expires at the end of this month. But Telkom has asked him to stay on as an advisor until the release of its full-year results in June.
Telkom, Africa's largest fixed-line operator has been hurt by a money losing Nigerian business and the decline of traditional telephony at home.
Moholi has 23 years experience in the ICT sector.
She first joined Telkom in 1994 where she spent 11 years, holding positions that included - group executive: regulatory affairs, managing executive: international and wholesale business, chief sales and marketing officer, and a member of the Telkom executive committee (Exco).
In 2005 she went to the Nedbank Group, then rejoined Telkom as MD of Telkom South Africa in May 2009.
Hedberg was appointed Telkom's acting group CEO in July last year. He took over from Reuben September, who in terms of his contract was supposed to leave in November 2010, but left abruptly at the beginning of July 2010.