Austria has proved a happy hunting ground for Frittelli, who won his first Challenge Tour event here four years ago at the Kärnten Golf Open presented by Mazda.
And after suffering play-off heartbreak in the Volvo China Open in April, the 27 year old now has a European Tour title to his name.
Frittelli began the day on seven under, two shots behind overnight leader Felipe Aguilar – who had led after each of the opening three rounds – but made gains at the first and third to grab a share of the lead.
He tapped in his close-range birdie putt at the fourth to take the outright lead before safely parring the next four holes.
Frittelli was joined at the summit by Mikko Korhonen after he carded his fourth birdie of the day at the ninth, but the South African knocked in his 15 foot putt at the ninth to get to 11 under and go one shot clear.
And when Finland’s Korhonen dropped a shot at the tenth, Frittelli was in possession of a two shot lead.
Frittelli gave himself a great birdie chance at the tenth but could not take it, missing his putt from two feet.
He did not let that close-range miss affect him though, rolling in his eight-foot birdie putt at the next before pulling off a good par save at the 13th.
Frittelli dropped his first shot of the day at the short 14th to sacrifice his outright lead and Kruger made back-to-back gains at the 15th and 16th to knock his countryman off the top of the leaderboard altogether.
But Frittelli fired his sixth birdie of the day at the 16th to get back to 12 under before saving par from eight feet at the next.
With Kruger dropping a shot at the last, Frittelli stood at the 18th tee with a one-shot lead, and he knocked in his close-range par putt to secure the trophy.
Frittelli eyeing rankings after win
Frittelli was thrilled to secure his first European Tour crown. He said: “I’m just elated.
“I’m really happy with the way the week went – super stoked to get my first win on the European Tour – I think it’s been a long time coming and I am glad to be inside the winner’s circle.
“I was just trying to get it on the green, make a par and avoid a play-off. My zero and two record in play-offs is not very good so I didn’t want to have extra guys in the play-off trying to beat them on the 18th.
“Hopefully I get into The Open with this performance and it should move me up the Race to Dubai and open up some more doors down the road.
“On 17 that was crucial. To get up-and-down there and leave myself with a par chance on the last for the win was definitely key.
“I was pretty relaxed through the back nine actually. I felt a lot more nervous in China and gained a lot from that experience having lost to Alex Levy in a play-off, but I felt good coming down the back nine and hit some really crucial shots, so I’m really proud of how I handled the nerves.”
Englishman Horsey, who matched the course record with a stunning 64 on Friday, posted the lowest round of the day once again on Sunday – carding seven birdies and no bogeys in a flawless 65.
The 32 year old opened his fourth round with four straight birdies before making another gain at the seventh to cover the front nine in 31 shots.
A number of important par saves kept Horsey’s challenge on track and he added further birdies at the 13th and 15th to get to 11 under.
After carding three birdies and a solitary bogey in his first ten holes, Kruger surged into contention when he holed his approach shot at the 12th for a brilliant eagle.
And he fired back-to-back birdies at the 15th and 16th to get to 12 under and grab the outright lead with two holes of his fourth round remaining.
But a disappointing bogey at the last saw him finish one shot behind Frittelli.
Korhonen made a superb start to his final round, notching four birdies on his front nine to get to ten under. He dropped his only shot of the day at the tenth but rolled in his eagle putt at the 16th to finish in a tie for second.
Richard McEvoy finished another shot back on ten under, while Aguilar posted a closing 75 to finish the week six shots behind Frittelli on six under.