The South African did not put a foot wrong on the Sunday afternoon, posting a spotless 66 that contained five birdies and some outstanding par saves to keep his card clean.
Coetzee began the day with a one shot advantage but was knocked off the top of the leaderboard early on after parring his opening six holes in a patient start to his final round.
The 34-year-old made his first birdie of the day from 20 feet on the difficult seventh before picking up another shot from a similar distance on the short eighth to get to 13 under and regain his one stroke lead.
After making another gain from nine feet at the 11th, Coetzee made key par putts on the 12th and 13th to remain in front as the chasing pack began to gather just behind him on an incredibly bunched leaderboard.
He then holed brilliant birdie putts at the 16th and 17th to move to 16 under par and give himself a two shot cushion heading to the 18th tee.
Coetzee saved his best drive until last and went on to make a nerveless par to win for the second week in a row, having also tasted victory at the Titleist Championship at Pretoria Country Club on the Sunshine Tour last week.
Englishman Laurie Canter finished alone in second on 14 under after he also made five birdies in a flawless 66, while his countryman and World Number 16, Tommy Fleetwood, was another stroke back in a tie for third with Swede Joakim Lagergren.
Coetzee made a steady start to his round, tapping in for par at the first before narrowly missing his close range birdie effort on the second.
After slipping from the top of the leaderboard, Coetzee produced a remarkable up-and-down from the thick rough by the sixth green to save par and limit the damage.
He regained the outright lead when he converted lengthy birdie putts at the seventh and eighth before getting up and down from the rough for another valuable par on the ninth.
Coetzee holed a nice birdie putt at the 11th before getting a lucky break on the 12th as his tee shot narrowly avoided the water. He chopped out of the thick stuff on the bank with his second shot before somehow finding the green with his third and going on to save par.
He made another good save from ten feet on the next before sending his tee shot on the short 16th to eight feet and tapping in his birdie putt to get to 15 under.
Another birdie followed at the par five 17th - from around ten feet - before a par at the last secured the trophy.
Coetzee’s previous European Tour victories all came in Africa and he was delighted to make his breakthrough on European soil.
He said: “(Winning in Europe) was the next step for me really.
“I have always had a list of things I wanted to achieve in my career as a golfer and originally I never thought I would get as far as winning on the European Tour, so ticking that box a while back was really nice, and then I started to realise that I was a bit comfortable playing back home and I needed to go to the next step and win away from home.
“And then I won in Mauritius, which still counts as a Sunshine Tour event, so I still felt like I needed to get off my continent and win something else.
“So I am just happy that I kind of ticked the box in the right order.
“I remember as an amateur I had to win a national stroke play event and then try and win one of the big three national match play events. I ended up winning the South African amateur match play before I won the stroke play event, and I felt like I needed to take a step back and figure out how to win a stroke play event.
“It is nice that I am ticking the boxes that I have set for myself.” European Tour