The 33-year-old Englishman went into the last round five shots ahead and carded a final round 70 to finish 20-under-par, three shots clear of Northern Ireland's Hoey, who tied for second place with South African Danie van Tonder.
Fisher led from the second round onwards at the Ernie Els-designed Copperleaf Golf and Country Estate course but he needed much fortitude in overcast conditions on the final day as Hoey closed the gap to a single shot at the 11th with a birdie after an attacking front nine.
But the next hole saw Hoey double bogey for Fisher to go back three ahead, from which point he never looked back.
"It was a testing day with the weather conditions so I was thrilled to get over line. My putting has been my Achilles heel for a while but I saw the lines all this week and really did well," Fisher said at the trophy presentation.
Hoey posted a final round 68, leaving him 17-under for his best ever Tour finish and sharing second prize with Van Tonder, whose 66 was the best round of the day.
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