Rescuers were called to the scene on the moor, near to White Wells, at about 1.10pm on Saturday, April 25.
On arrival the team determined that the man's situation was "critical".
An air ambulance was called.
A spokesman for the Upper Wharfedale Fell Rescue Association said: "The team was called today to assist the YAS in treating a male mountain biker who had crashed on Ilkley Moor, near to White Wells.
"On arrival at the scene it was apparent that the casualty’s situation was critical and the Yorkshire Air Ambulance was called.
"The biker, initially unconscious, had suffered severe facial & head trauma and required immediate evacuation to hospital.
"The air & land ambulance medics quickly and efficiently stabilised the patient and the UWFRA team scooped and carried him to the waiting road ambulance.
"The team wish the biker all the very best and to a rapid and successful recovery."
A Yorkshire Air Ambulance spokeswoman said: "We were called to a male patient with severe head trauma as a result of a mountain bike fall.
"The patient was taken by road ambulance, accompanied by our Critical Care Team to Leeds General Infirmary."