PRETORIA, March 2, 2014 (AFP) - The 33-year-old Englishman finished with a two-under-par 70 on a wet, murky afternoon to win from Northern Irishman Michael Hoey and South African Danie van Tonder.
Fisher, whose last triumph came at the 2010 Irish Open, sealed first place with an eagle three on 15, his medium-distance left-to-right putt always on course for the pin.
It gave him a four-shot cushion at the par-72, 7,281-metre (7,964-yard) The Els Club Copperleaf, the longest European circuit layout.
"My target was a sub-70 final round and I fell just short after a bogey five on the last," Fisher told reporters.
"It was testing out there owing to the weather conditions so I am thrilled to be champion. I had a couple of wobbles but always believed the trophy would be mine.
"The 15th was the key hole. It was my second birdie of the tournament there and I felt confident about the putt after taking my time reading the line.
"Putting has been my Achilles heel for many, many years, but I loved the greens here and got the lines correct most of the time."
The Englishman, ranked 82 in the world, was a model of consistency over the course west of Highveld city Pretoria, shooting rounds of 66, 65, 67 and 70 for a 20-under 268 total.
He trailed compatriot Simon Dyson and South African Trevor Fisher junior by one shot following the opening round, took the second-round lead and was never headed during the weekend.
Hoey did slash the five-stroke overnight advantage of Fisher to a single shot after 11 holes by sinking a long birdie-three putt.
But the Irishman found water with his approach shot at the next hole, was punished with a double-bogey six and slipped three strokes off the pace.
Hoey closed with a 68 and Van Tonder had a six-birdie 66 -- the lowest score of the final round of the last of eight European Tour tournaments hosted by South Africa.
Spaniard Carlos Del Moral (68), seeking a maiden European victory, also came within a shot of Fisher, but his inconsistency prevented a sustained challenge and he came fourth.
Leading scores after final round of European Tour-Sunshine Tour co-sanctioned Tshwane Open golf tournament at par-72, 7,281-metre (7,964-yard) The Els Club Copperleaf near Pretoria Sunday (RSA unless noted):
268 - Ross Fisher (ENG) 66-65-67-70
271 - Michael Hoey (NIR) 69-65-69-68, Danie van Tonder 66-70-69-66
272 - Carlos Del Moral (ESP) 68-65-71-68
273 - Hennie Otto 71-65-69-68
275 - Darren Fichardt 66-68-70-71, Kevin Phelan (IRL) 68-69-68-70, Chris Wood (ENG) 67-68-72-68