EAST LONDON, 7 Mar 2015 (AFP) - The 35-year-old Johannesburg-based professional picked up an eagle and two birdies on the outward nine at a windy par-72 East London Golf Club course.
And birdies on five of the last eight holes equalled the lowest score of the week after German Maximilian Kieffer carded a second-round 63 Friday.
Fisher is two shots ahead of halfway leader Matt Ford (69) with a double-bogey six at eight proving costly for the Englishman.
Another South African, Jaco van Zyl (68), is two shots further back and would have been closer to Fisher had he sunk several short putts.
Spaniards Jorge Campillo (67) and Eduardo de la Riva (72), Dane Morten Madsen (64) and Englishman John Parry (69) are six shots off the pace.
South Africans have won every edition of the Africa Open since its 2008 debut, with the event joining the European Tour two seasons later.
The two previous title-holders in the field this year, Darren Fichardt and Shaun Norris, each carded a 73 and they are out of contention for first prize.
"I played solid, but did not expect to shoot a 63 in such tough conditions," admitted Fisher, who has won eight Sunshine Tour events but is chasing a maiden European Tour success.
"I will play my own game in the final round, taking it shot by shot. I will try not to get ahead of myself too much."
Ford, who qualified for the European Tour last November after 10 attempts, came badly unstuck at the par-four eighth.
After bunkering his approach shot, he took three more to get on the green before holing a tricky putt.
Northern Irishman Darren Clarke, who will skipper Europe in the 2016 Ryder Cup clash with the United States, had a 72 and is 12 strokes behind Fisher.
Leading Africa Open third-round scores Saturday at the par-72, 6,108-metre (6,679-yard) East London Golf Club (RSA unless noted):
200 - Trevor Fisher jnr 69-68-63
202 - Matt Ford (ENG) 67-66-69
204 - Jaco van Zyl 70-66-68
206 - Jorge Campillo (ESP) 71-68-67, Morten Madsen (DEN) 71-71-64, John Parry (ENG) 68-69-69, Eduardo de la Riva (ESP) 68-66-72
207 - Joakim Lagergren (SWE) 72-67-68, Mark Tullo (CHI) 70-67-70
208 - Dean Burmester 72-66-70, Gregory Havret (FRA) 69-67-72, Keith Horne 72-68-68, David Howell (ENG) 68-69-71, Jean Hugo 72-67-69, Maximilian Kieffer (GER) 74-63-71, Mikko Korhonen (FIN) 73-69-66, Julien Quesne (FRA) 70-72-66, Justin Walters 70-70-68