The South African started the final day at Royal Golf Club with a two-shot lead, but was overtaken at the turn and two-over for the day after 12 holes as a host of players staked a claim for the trophy.
Frittelli is not a winner on the DP World, PGA and European Challenge Tours without possessing a steely resolve, though, and he made three birdies in four holes from the 13th, signing for a 71 and finishing at 13-under.
Countryman Zander Lombard and Swede Jesper Svensson were his nearest challengers after rounds of 68 and 70 respectively, two shots clear of another South African in Ockie Strydom and Frenchman Frederic Lacroix.
Fine amateur career
Frittelli enjoyed a fine amateur career, holing the winning putt as the University of Texas won the national collegiate championship in the United States in 2012.
A Challenge Tour graduate in 2016, he won the Lyoness Open and the AfrAsia Bank Mauritius Open in 2017 before moving to the PGA Tour and taking the title at the 2019 John Derre Classic.
After a difficult 2023 which left him contemplating his future, he said this week he was "invigorated" to be back on the DP World Tour after taking up a route for those who finished outside the top 125 on the FedExCup Fall Points List and he has now been rewarded with a first worldwide victory since the summer of 2019.
"It feels great, it feels awesome," said Frittelli, who missed the cut or withdrew from 23 of his 27 starts on the PGA Tour last season.
"It's been a long road the last five or six years since I left the DP World Tour and went to the States. It was a pretty tough year last year in America but it feels awesome to back on top right now.
"Last year I was in a couple of spots where I thought I was giving the game up to be honest and looking for something else.
"I found some resolve at the end of last year and got some good work from my physio and my coaches and trainers. I'm glad I persevered and all the support from family and friends has been well worth it.”
He added: "I think it shows my mental toughness, it shows the focus I have and those things that you can't really quantify. I was swinging it great all week and then all of a sudden couldn't hit it on the planet on the Sunday round so I'm glad I managed to have the resolve."