The 23-year-old, who started the day with a two-shot lead, closed with a double-bogey 6 on the tough 18th hole at the Greg Norman-designed Ayla Golf Club.
But, helped by making four birdies in six holes as he got off to a fast start in the final round, Lumsden held on for a one-shot victory over England's Curtis Knipes in the $75,000 event.
“Don’t ask me about the 18th," said a relieved Lumsden afterwards, before adding: "I am delighted to get the win. I felt really good about my game the whole day and got off to a good start.
“I then went through a little bit of a rough patch on the back nine, but I was able to make some good swings after that. I will think back about the 18th hole and process what I did wrong there, but very happy to get the job done and hopefully we can carry it on from here."
Lumsden, who is in his first full season in the professional ranks, joins Paul Doherty, Clarke Lutton, David Law and Bob MacIntyre in tasting victory on the third-tier circuit.
MacIntyre won the Sahara Kuwait Championship in just his second pro start, using that success as a springboard to become European Tour Rookie of the Year last season.
London-based Lumsden, who picked up a cheque for $13,500, reached the final of the 2017 Scottish Amateur Championship, losing to Sam Locke in the final at Prestwick.
He used a spell at Northwestern University in Chicago to hone his game and also become the first Great Britain & Ireland golfer to receive the Byron Nelson Award.
Presented by the Golf Coaches Association of America, Lumsden's reward for that includes an appearance in the AT&T Byron Nelson Classic on the PGA Tour in May.
“There wasn’t one defining or key moment today," added Lumsden, who was born in London and is a member at Royal Wimbledon but jumped at the chance to represent Scotland through his Edinburgh-born grandparents.
"I just played solid golf throughout.”