Saint Dragon is a horizontally scrolling shoot 'em up where you take on the role of St. Dragon, a cyborg warrior fighting against an alien invasion that has enslaved many races in the galaxy. The Cyborg Monsters, designed by humans, have superior firepower and attack capabilities, but can only be defeated by one of their own kind.
The game features five R-type-style levels with a variety of weapons to use, and although losing a life will mean starting over from scratch, you won't lose any of your power-up weaponry. The game's unique feature is the armoured tail that serves as both a shield and a deadly weapon, which can be used to ward off attackers and deal significant damage.