A laser sighting device for a firearm and a method for mounting a laser sighting device on a firearm. A laser sighting device for a firearm comprises a holder adapted to attach to the handgrip of the firearm such that the firearm may be held in a firing position by the handgrip with the device installed thereon, the holder including a first compartment for receiving a laser and holding the laser so as to propagate a beam of light substantially in the muzzle direction of the firearm, and a second compartment for receiving a battery to power the laser, a switch for activation of the laser by the user's hand holding the handgrip in firing position, and an electrical circuit disposed within the holder for interconnecting a laser disposed in the first compartment, a battery disposed in the second compartment and the switch.