Abstract: This invention relates to a bicycle brake light switch control assembly for use to mount on most of all types of bicycle brakes to control turning on/off of an associated bicycle brake light in accordance with the operation of the associated bicycle brake. Upon applying the brakes of a bicycle, brake cables are contracted, forcing a sliding sleeve of the invention to displace further into a socket. This causes two conductive plate springs to come into contact with a conductive tube, thereby completing an electric circuit and inducing the brake light to turn on. When the brake is released, springing means forces the sliding sleeve to displace to its original position. This drives the two conductive plate springs away from contact with the conductive tube. This breaks the electric circuit and the brake light turns off. The sliding sleeve contains two water-proof retainer rings to permit the invention to operate in wet conditions.