Deputies responded to a bridge on New Light Road near Ghoston Road just before 6 p.m.
When deputies arrived, the child was pulled from the water by first responders and transported to WakeMed.
The child was later pronounced dead.
Two family members who had tried to rescue the child were also taken to WakeMed with injuries that did not appear to be serious, according to the sheriff's office.
Deputies are interviewing witnesses to try to determine what happened before the tragedy.