The appointment follows the resignation of Brian Molefe earlier this month as Group Chief Executive Officer of the company.
Koko is current Group Executive: Generation and has held various positions since he joined Eskom in 1996. He will take up his new position from 1 December 2016.
"I approved the Board’s request to appoint Mr Koko as acting Group Chief Executive Officer. Mr Koko has a wealth of experience and understands the challenges Eskom faces. His appointment will also ensure continuity at Eskom," Brown stated in a media statement.
"I have also asked the Board to immediately start the process to appoint a permanent Group CEO and that this process needs their urgent attention."
"Koko must ensure that the current trajectory at Eskom continues,” she added.
Brown : I have also asked the Board to immediately start the process to appoint a permanent Group CEO. #Eskom— KhayelihleKhumalo (@KhayaJames) November 30, 2016