Around 8:15 p.m., Corporal Thomas Chaney was standing outside his police cruiser along Ovilla Road and Dorothy Lane when he was hit.
One of the lanes was blocked off as Chaney was investigating a minor crash, and it appears that he was clipped by a maroon SUV that was trying to pass him, police said.
The officer fell and sustained injuries including broken teeth and some head trauma.
He was taken via CareFlite to Methodist Hospital in Dallas with non-life-threatening injuries and his condition was upgraded from serious to fair on Thursday.
The driver of the SUV stopped and tried to help the officer.
Chaney is a 17-year police veteran.