Smith, from Bath, won at the second extra hole after finishing tied with defending champion Alex Levy on 13 under, but only after the Frenchman had missed a putt to win from inside three feet on the pair’s first trip back down the 18th.
Twenty-four-year-old Smith, who held a two-shot lead overnight, began his final round with a birdie, but dropped shots on the sixth and eighth to leave the door ajar for Levy, who shot a closing 69, to challenge for the lead on the back nine.
Smith regained the lead with a birdie from three feet at the 11th before leaving his bunker shot at the 13th short where he missed a 20ft putt for par.
Levy and Smith both birdied the 15th and it was the former who went ahead with another gain at the next, only for Smith to get up-and-down at the last to force a play-off with a round of 71.
Levy then missed a three-foot birdie effort as they replayed the 18th hole, but when Smith was presented with a similar opportunity on the next journey down the last he made no mistake.
Sweden’s Johan Edfors (70) and Bangladesh’s Siddikur Rahman (68) finished tied for third on 11 under, while Scotland’s Richie Ramsay and England’s Ashley Chesters both recorded top-ten finishes.
Woodsome Hall’s Chris Hanson finished in a tie for 19th place and took his year’s earnings up to €271,018 with a cheque for €22,066 in Germany.
After a two-under-par 70 on Saturday he began yesterday with three successive birdies.
He added a further three birdies, but also four bogeys as he carded another 70, the score with which he had opened in Hamburg before adding a level-par 72 on Friday.
Malton’s Simon Dyson was just a shot behind Hanson going into the weekend (71 72), but slipped back on Saturday with a 78, in which he had six bogeys and a double bogey.
Two birdies in his final round were offset by a double bogey as he ended his week’s work with a 72 to win €3,725.
After tclinching his maiden victory, Smith said: “I’ve loved it. It’s been nerve-wracking at times, but I’ve really enjoyed it.
“It’s all a bit surreal. Obviously the Challenge Tour last year and the EuroPro the year before that. It’s been fun.
“I had a really good start to the year and the first aim was just to secure my Tour card, which I managed to do.
“And then the second goal was to win an event, which I’ve managed to do.”