The handgun identification light is a device attachable to a handgun, the device illuminating the handgun with flashing blue and red lights to provide advanced real-time early warning to police officers who encounter a fellow off-duty plainclothes or undercover officer during their response to the commission of a crime. The device has an on-off switch connected to a battery and flashing LED's disposed along opposing sides of the device. The device includes a tilt switch, grip switch, or gun motion sensor that detects when a user draws the weapon. By activation of the flashing red and blue light device on his weapon, an off-duty plainclothes or undercover police officer who draws the weapon becomes readily identifiable by other officers in proximity as a fellow law officer, thus avoiding misidentification and tragically resultant friendly fire incidents.