The purpose of this study is to understand the injury mechanism of the cyclist’s head and lower extremity in car‐to‐cyclist accidents. The kinematic behavior of the whole body and the interaction of car, cyclist and bicycle were numerically investigated using a simulation with FE models of the human, bicycle and car. In addition, protection performance of a helmet for A‐pillar impact was examined with FE models of a human head, a helmet and a car. The upper body of the cyclist dropped toward the bonnet with the hip rotating on the bonnet and the upper body twisting due to the interaction between the front structure of the car and bicycle. The knee of the cyclist made contact with the bonnet leading edge and shear loading was generated resulting in ruptured knee ligaments. It was found from head impact simulations that the liner of the helmet deformed locally and bottomed out in high speed impact and as a result, high deceleration on the headform impactor was generated despite wearing the helmet. However, the helmet can prevent skull fracture and brain strain significantly. Therefore, it is concluded that there is a potential that helmets can protect the head in impacts against the A‐pillar.