Abstract: A Keyway Trigger System with a dry fire prevention nock is provided for use in a crossbow. The System ensures proper, full engagement of the dry fire prevention nock with a crossbow string such that the crossbow will only fire when an arrow is loaded correctly. The nock is received in a slotted opening forming a keyway adapted to be engaged by surfaces of the profiled dry fire prevention nock such that only when an arrow is properly loaded into the keyway, aligned with trigger latch members and fully engaged with the crossbow string then the trigger moves from a non-firing position to a firing position allowing the arrow to be fired. The Keyway Trigger System prevents dry fire and partial dry fire, eliminates risk of damage to the crossbow, eliminates potential risk of injury to a user, and improves accuracy and reliability of the flight trajectory of the arrow.