Overnight leader Stenson had recovered from an air shot on the second for a three-shot lead with three to play, but a three-putt bogey on the 16th gave Leishman a way through and two final birdies gave the Australian a six-under par 66.
Stenson's frustration boiled over up as he slammed his bag to the ground after landing in the fairway bunker with his tee shot on the last, with the world number seven blaming the way the sand had been raked.
A bogey meant the Swede had to settle for a 70 to finish 13 under par, with South African Jaco van Zyl on 10 under and American Robert Streb a shot further back.
“It was disappointing on the last to find a shocking rake job in the bunker. It was sitting down in a hole and I couldn't even get my lob wedge back onto the fairway,” said Stenson, who had spend three days recovering from flu prior to the event.
“I was feeling better when I started but playing in 38 degrees certainly takes it out of you, so after the first 10, 11 holes I was really struggling.
“All in all I didn't play very well today and the short game and the putter kept the score together and that's why I'm still at the races tomorrow.”
Leishman, who lost out in a three-man play-off for the British Open at St Andrews in July, said: “I saw Henrik was getting away a little bit so I had to try to do something to make it interesting for tomorrow.”
“Hopefully I can have another good round like today and give him a run for his money.”– AFP
Original source: Leishman leads NGC