Trigger lock, safety and alarm devices for a firearm includes a trigger clamp that immobilizes the devices on the firearm in a position in which the device cannot be moved with respect to the firearm to actuate the trigger and discharge the firearm. The devices include a locking mechanism that is used to mount the device to the firearm. An alarm on the device is sounded by actuation of a motion sensor when the device is moved, for example, when the firearm is moved. The alarm can be enabled and disabled using buttons mounted on the devices, and an indicator light flashes on the devices when the alarm is enabled. The keys are also used to operate the locking mechanism to lock or unlock the devices.