Scotland's Jamieson struck five birdies, including one on the final hole, to finish on an 11-under-par total.
Irishman Lowry and Belgium's Pieters, who matched each other with bogey-free rounds of five-under 67, piled the pressure on Jamieson but the Scot showed great composure in his fight for a second title on the European Tour.
"After yesterday, certainly the whole day seems a little more straightforward but it still wasn't easy," Jamieson, who won his first title in 2013, said.
"The greens were considerably quicker and there was still a decent amount of breeze.
"It would be massive, a game-changer, to win a tournament of this stature. There's definitely been some great champions here, and that's an awful long way to go."
India's Shubhankar Sharma and Norway's Viktor Hovland sat in a share of fourth place on eight-under, while Spain's Rafa Cabrera Bello was a shot further back alongside Englishmen James Morrison and Ian Poulter.