The ammunition used in the marker, paintballs are spherical gelatin capsules containing primarily polyethylene glycol, other non-toxic and water-soluble substances, and dye.

The quality of paintballs is dependent on the brittleness of the ball's shell, the roundness of the sphere, and the thickness of the fill; higher-quality balls are almost perfectly spherical, with a very thin shell to guarantee breaking upon impact, and a thick, brightly colored fill that is difficult to hide or wipe off during the game.

The highest-grade paintballs incorporate cornstarch and metallic flake into the fill to leave a thick glittery "splat" that is very obvious against any background color, and hard to wipe off. Almost all Paintballs in use today are biodegradeable. All ingredients used in the making of a Paintball are food grade quality and are harmless to the participants and environment.