It happened around 9:30 a.m. on Ervin McGarrah Road east of Lowell.
According to the sheriff's office, someone called 911 and said he saw a mule dragging a small child.
When deputies arrived, family members were giving CPR to the girl.
She was taken to Northwest Medical Center in Springdale.
Investigators say the child was being watched by her grandfather while her father was sleeping.
She was trying to ride a mule the family owned, and had ridden many times before.
According to deputies, the seven-year-old tied the lead rope around her waist, and the mule was spooked at some point, throwing the girl to the ground.
Investigators say the mule dragged her around the property until it got tangled up and stopped.
The child died from her injuries at the hospital.
Sheriff's deputies are investigating the incident.