After two missed cuts in Abu Dhabi and Dubai, the Lothians star ended the European Tour's Middle East Swing on a high as he carded eight birdies in a closing 66 at Royal Greens on the Red Sea coast.
The four-under-par effort lifted him into a tie for 21st behind the winner at the King Abdullah Economic City course, Northern Ireland's Graeme McDowell.
"It's as good as I have played for a long time," said the three-time tour winner after recording his best finish since winning the Hero Indian Open just under a year ago.
"I got some good signs yesterday, when I was a bit disappointed as I played better than my score. I played lovely today and could have shot 60 today as I hit it really well.
"At the two par-5s, I was inside 15 feet for eagle and probably missed six putts inside six foot, though, in fairness, they are so hard to read.
"I got better as the week went on and I am delighted with that for a finish. It's a great one for me to build on when I come back out for Oman and Qatar and then my title defence in India."
Capital-based Richie Ramsay was equally pleased with his day's work as he finished alongside Gallacher after a closing 68.
"It was nearly a great day as I played really good," he said. "I missed the first fairway by a yard but hit some irons shots and the only putt I really holed was a nice one on the last from about 12 feet.
"It was probably the best round I've played in the Middle East Swing as I felt I had full control out there and it was tricky out there at times in crosswinds."
In contrast to both Gallacher and Ramsay, Grant Forrest was disappointed to slip from joint-10th at the start of the day to tied for 27th following a 73.
"I didn’t do much wrong at all and it just doesn’t feel like I shot three-over," he said. Referring to a similar last day in Dubai, he added: "It's frustrating not finishing a tournament off well."
Connor Syme, who has made the cut in all four of his events so far back on the main tour, closed with 73 to end up joint-52nd on two-over, two shots ahead of Scott Jamieson (73).