A year-long investigation has found that allegations of bribery by Turkish cellphone operator Turkcell against MTN are unfounded, the South African company said on Friday.
The probe had cleared MTN's former group president and CEO Phuthuma Nhleko and its former commercial director Irene Charnley, said MTN chairman Cyril Ramaphosa.
"Allegations of complicity against the chairman and the group president and [current] CEO Sifiso Dabengwa were similarly found to be without substance," he said.
The Turkish mobile operator Turkcell filed a US4 billion (about R35.5bn) lawsuit against MTN in a United States court last year.
It accused MTN of bribing Iranians and South Africans to acquire a mobile phone licence in Iran. Turkcell claimed that it initially had acquired the licence.
On Friday, Ramaphosa said the MTN board commissioned South African-born British judge Lord Hoffmann to investigate the allegations. His findings were presented to the MTN board.
"Lord Hoffmann's committee has determined that the Turkcell allegations are without foundation," Ramaphosa said.
"Lord Hoffmann concluded that he found nothing in the conduct of MTN over this period that puts at question MTN's integrity or propriety. This is a reassuring validation of MTN's culture and ethical business practices."
MTN said it expected the lawsuit in the US to be thrown out as soon as the supreme court had made its decision.