Emergency responders were called to the home at 3615 Pilson Road, Sanford around 5:43 p.m.
Detectives say the parents, Lierin Lindquist and Bruce "Tyler" Murchison of 772 Red Branch Road in Carthage, told them they were at Murchison's father's home visiting the boy when they lost sight of him.
The child was found a short time later in a 4-foot-deep swimming pool connected to the home by a deck.
The boy's body was sent to UNC Hospital for an autopsy. The investigation is ongoing.