The Scotsman birdied three of his last five holes at Leopard Creek Country Club to sign for a 67 and put the pressure on David Lipsky but the American held his nerve to take the title by two shots.
The result was Drysdale's second top five in four events so far this season and moved him up to third in the early Race to Dubai Rankings presented by Rolex.
The 43 year old has been an ever-present on Tour since graduating from the Challenge Tour in 2004, with three trips to the Qualifying School and two other second-places along the way.
His 471 events without a win is the longest active streak on Tour and just 15 short of Ross Drummond's all-time record, but Drysdale will head into Christmas seemingly closer than ever to a victory.
“I would have taken it at the start of the week,” he said. “Overall a good performance. A couple of lucky breaks here and there but overall delighted with my week.
“From tee to green, the last two or three months have been good. The putting has been a little bit erratic now and again but I holed my fair share this week. I was steady off the tee and hit a lot of good iron shots.
“I took that shot on at the last trying to make a three and you never know what might happen.”
Zander Lombard emerged as Lipsky's closest challenger on the back nine, holing a bunker shot on the tenth and birdieing the 11th, making an eagle after a stunning second to 20 feet on the 13th and birdieing the next to cut the lead to one.
A triple-bogey after twice finding water on the 16th ended his hopes of a victory but the share for third is still an encouraging result for a player who finished as joint winner after going to the Qualifying School in November.
“I said to my caddie on the tenth tee, 'we're starting a new game',” he said. “This is why we play golf, being in contention on a Sunday on the last nine.
“I hit a poor second shot on ten, it just ballooned into the wind, but hit a fantastic bunker shot and got the ball rolling, got a little bit of confidence.
“I made a good birdie on 11, flushed a four iron to 20 feet on 13 for the eagle which really put me in the mix. On 16 I misjudged the wind twice, it happens, you don't try and do it but it's that type of hole.
“All in all I'm happy with it and it's good way to cap off the end of the year.
“It's time to go on holiday. Put the clubs away for a few weeks and then get back to Abu Dhabi.”