Effectiveness of ventilated helmets in providing thermal comfort to a motorcycle rider is studied. Computational fluid dynamics (CFD) simulations of human thermoregulation system and the air flow in the air gap of a full face motorcycle helmet are carried out. The thermal comfort of a rider is predicted using apparent temperature (AT) and wet bulb global temperature (WBGT) heat indices. The effect of an increase in ambient temperature and relative humidity of air, on the air flow and temperature in the region above the head is studied, to predict the thermal comfort of the rider wearing full face helmets. The effect of increasing the air gap between the head and the helmet is also studied. The results are then compared with the conditions when the rider is not wearing helmet. It is observed that the ventilated helmet is effective in providing thermal comfort to the rider only if the ambient air temperature is less than normal body temperature. For air temperature higher than the body temperature, vents do not provide any cooling to the head and the non ventilated helmet is more comfortable. Furthermore CFD simulations are performed to investigate the effect of increase in relative humidity in the ambient air on the thermal comfort of the rider. The increase in relative humidity of air from 50% to 90% at a fixed ambient air temperature, leads to an increase in AT and WBGT, indicating reduced thermal comfort of the rider.