It happened shortly after 9.30pm on Friday (September 17) on Sutton Lane, Keighley, near the junction with Knott Lane.
Police believe a white van hit a nine-year-old boy and another pedestrian, before it was driven away from the scene of the crash.
Emergency services, including the air ambulance, were called out but despite medical treatment, the boy was pronounced dead on the roadside.
A 49-year-old man later turned up at a police station in North Yorkshire and has been arrested on suspicion of causing death by dangerous driving.
He remains in police custody.
Detective Sergeant Fiona Allan, of West Yorkshire Police’s Major Collision Enquiry Team, said: “A nine-year-old boy has tragically lost his life and our top priority is supporting his family and ensuring that a thorough investigation is carried out into the events that have led to his death.
“This collision has happened right on the border of West Yorkshire and North Yorkshire and we are keen to speak to anyone who has witnessed this collision or who believes they may have seen the van involved immediately prior to or following this incident.”
Information can be passed to the Major Collision Enquiry Team via 101 or 101 Live Chat on the West Yorkshire Police website, quoting crime reference 13210474457.