Viewed from the front and the side, the Rat Terrier's head forms a blunt wedge shape. The skull is broad and slightly domed. It tapers slightly toward the muzzle. The jaws are powerful with well-muscled cheeks. Jaws are powerful and hinged well back allowing the dog to open his mouth wide enough to catch rats and other rodents.
Lips are dry and tight with no flews.
Lip pigment matches nose pigment. The Rat Terrier has a complete set of good-sized, evenly spaced, white teeth. A scissors bite is preferred but a level bite is acceptable. The nose is black or self-colored. Eyes are set obliquely and are round, small, and somewhat prominent.