In VanSlug: X Mission the player takes control of the titular hero, a futuristic detective named Van Slug whose hobby is to don his protective gear and rid the city and adjacent rural areas of monsters. In this platform shooter the player guides Van Slug through fairly vast levels populated by ground-based and flying enemies.

The hero's default gun with unlimited ammunition can be exchanged for stronger ones (but with limited ammo) by picking a correspondent power-up. Other power-ups include shields that further protect the hero from attacks, dynamite, and health-restoring items. A boss battle awaits Van Slug at the end of each stage.

Even though a bar entitled "EXP" is displayed alongside with the protagonist's health and special ammunition gauges, it never fills up and remains empty for the duration of the game.