The American made six birdies to finish on 17-under-par, ahead of Harris English in second, while Ryan Palmer and Webb Simpson ended tied-third.
Victory was 22-year-old Spieth's eighth PGA Tour triumph and the first in his home state of Texas.
"That is a tough hump to get over. To win in front of my home fans, what a great week," said Spieth.
Leading by one shot overnight, Spieth levelled through the first nine, before making six birdies on the back nine.
Spieth, who is from Dallas just 33 miles away from the course, is the youngest eight-time winner in 86 years since Horton Smith.
He is also the second youngest eight-time winner in PGA history.
Spieth, who is from Dallas just 33 miles away from the course, is the youngest eight-time winner in 86 years since Horton Smith.
He is also the second youngest eight-time winner in PGA history.
