Forest Hill Police Chief Dan Dennis said he terminated Sgt. Richardson Wolfe, who had been with the department since 2012, for "ineptitude."
"After looking at all of it, I wouldn't have wanted him to respond to the call if it was my 8-year-old, so I can't keep him on staff," Dennis told WFAA-TV. "Obviously I wish this had gone differently; obviously I'm disappointed in the officer involved."
The news came hours after Michael Webb, 51, was indicted in the federal kidnapping case.
Wolfe can appeal the firing. Efforts to reach him for comment on Thursday were unsuccessful.
Webb allegedly kidnapped the girl on May 18 when he reportedly grabbed her in front of her mother in Fort Worth and put her into his car. Forest Hill police received a tip that she was being held in a hotel the next day.
Responding officers spoke with Webb and made a visual inspection of the room; they left without finding the girl.
A separate tip led police to the hotel later that evening, and she was found with the suspect, police said.
Webb is charged with one count of aggravated kidnapping and six counts of sexual assault on a child.
He remains in federal custody.