It is the latest surprise political move after Zuma sacked his respected finance minister in a cabinet purge in March.
Brian Molefe, a close ally of President Jacob Zuma, resigned from Eskom and was sworn in as a member of parliament, with many observers expecting him to be promoted into the cabinet.
But on Friday he stepped down as a lawmaker and was re-appointed to Eskom, in the latest surprise political move after Zuma sacked his respected finance minister in a cabinet purge in March.
"Definitely‚ he is coming back on Monday," Eskom board spokesman Khulani Qoma told local media.
Qoma said Molefe was re-appointed because the corruption report that forced his resignation was "not conclusive" and also due to a dispute over his proposed 30 million rand ($2.2 million) pay-off.
"The board decided to rescind its initial decision to grant him early retirement," he said.
Molefe was implicated in a public ombudsman report detailing corruption involving the wealthy Gupta business family, who are alleged to have influence over Zuma.
Respected finance minister Pravin Gordhan, seen as bulwark against corruption, was sacked in March in a reshuffle announced at midnight.
The sacking caused the rand to plummet and the country's sovereign credit rating was downgraded to "junk status" by global agencies Standard & Poor's and Fitch.
It also triggered unprecedented criticism from within the ruling African National Congress and spawned public protests calling for Zuma to leave office.
The ombudsman report revealed Molefe's extensive contact with the Guptas when they were in the process of acquiring a mine that supplies Eskom with coal.
Molefe denied any wrongdoing but resigned as Eskom chief.