The boy was flown to hospital by air ambulance following the crash on November 19, but died in the early hours of the following morning.
The crash, which happened at around 5.30pm on the A170 between Kirkbymoorside and Beadlam, involved the cyclist and a grey Volkswagen Tiguan.
A spokesman for North Yorkshire Police said: "The road was closed for several hours to allow our officers to carry out investigation work at the scene of the incident. The driver of the Volkswagen Tiguan is assisting police with their enquiries.
"We’re now appealing to anyone who was in the area at the time who has any information that could help with our investigation. We believe that both the car and the bicycle had travelled from Kirkbymoorside.
"Did you witness the collision? Or do you have any dash camera footage that may have captured something leading up to the collision or the collision itself?
"If you can help, please email [email protected] or call North Yorkshire Police on 101, select option 2, and ask for Jon Moss. Please quote the North Yorkshire Police reference number 12210245050."