The 43-year-old, who finished fourth in the event in 2016, hit eight birdies to return a bogey-free round.
Dredge's round of 64 is his best since regaining his tour card last year.
Meanwhile, former US Open champion Graeme McDowell of Northern Ireland started well and finished the day two strokes back in third.
McDowell opened with three birdies and reached the turn in only 30 shots after starting on the 10th tee.
The 37-year-old dropped just one shot, on the sixth, as he signed for a six-under 66.
"I understood today that the scoring was going to be good," Dredge said.
"It was an opportunity to go at more flags and get the ball closer to the hole.
"Without the wind, it certainly makes it a lot easier to get the score going and get the putts in."
Find out how to get into golf with our special guide.
Welsh golfer Bradley Dredge carded an eight-under-par 64 in the opening round to lead the Qatar Masters by one shot over Finland's Mikko Korhonen.