The boy was running down the sidewalk with his father in the 700 block of Clark Street, when he fell at the end of a driveway, Tumwater police said.
At the same time, a pickup truck was backing up an incline and out of the driveway. The driver didn't see the boy and ran over his torso, police said.
The boy was still conscious and talking, but was flown by helicopter to Harborview Medical Center in Seattle to be evaluated and his condition is not known.
Police say it doesn't appear the driver was impaired. Their investigation is still ongoing.