The supraorbital arches over the eyes are moderately well defined. The muzzle is broad, blunt, and deep with a very slight taper from the stop to the nose. The length of the muzzle is equal to approximately 45 percent of the length of the head. Jaws are very powerful. The nasal bridge is straight.
Lips are thick and tight in front, with dark pigment.
Beginning just behind the canines, the lower lips become visible and increasingly pendulous as they reach the corner of the mouth. The Tosa Ken has a complete set of large, evenly spaced, white teeth meeting in a scissors bite. The pigment inside the mouth is black, with a dark roof being desirable. The tongue may be pink, or pink with bluish-black spotting. Judges should not penalize missing incisors provided that there is sufficient space for a full complement of incisors.