The Cathkin Braes member, who four years ago was plying his trade on the third-tier PGA EuroPro circuit, held off Englishman Steve Webster and Eduardo de la Riva of Spain in a play-off to win the first event on the 2013 Race to Dubai.
In a tournament cut to 36 holes on a Royal Durban course reduced to a par 65 because of saturated fairways, Jamieson shot a closing eight-under-par 57 to surge to the top of the leaderboard with a seven-under aggregate of 123 before emerging triumphant in the sudden-death shoot-out.
De la Riva bogeyed the first play-off hole and then, in fast-fading light, Webster, the only one of the trio to have won on the circuit before, did the same after they had returned to the 18th tee.
Jamieson's sparkling eight-birdie 57 will not go into the European Tour record books given the huge modifications to the course but the 29-year-old will not worry about that. The Scot will still be marked down as a European Tour champion and his win gives him a two-year exemption for the main circuit.
Jamieson, six shots off the lead heading into the final day, said: "It was a strange day. First thing this morning, I didn't think I'd end up standing with the trophy."
De la Riva and Webster had set the clubhouse target before Jamieson joined them with a rousing charge that was bolstered by an outward half of 26. The trio then had to wait several hours to see if any of the later starters would pass them.
Jamieson, who had three top-three finishes in 2011, his rookie season on the European Tour, added: "I knew I needed a fast start and was lucky enough to get that.
"Of course there were nerves in the play-off. But that's why we play – to get into that situation, and that's what I kept telling myself. Those guys would have been nervous too. It's just a question of who plays the best golf."