The skull is square, flat on top, free from wrinkles, cheeks flat, brow abrupt and the stop well defined. The ideal Boston Terrier expression is alert and kind, indicating a high degree of intelligence. This is a most important characteristic of the breed.
The eyes are wide apart, large and round and dark in color. The eyes are set square in the skull and the outside corners are on a line with the cheeks as viewed from the front.
The ears are small, carried erect, either natural or cropped to conform to the shape of the head and situated as near to the corners of the skull as possible.
The muzzle is short, square, wide and deep and in proportion to the skull. It is free from wrinkles, shorter in length than in width or depth; not exceeding in length approximately one-third of the length of the skull. The muzzle from stop to end of the nose is parallel to the top of the skull.
The nose is black and wide, with a well defined line between the nostrils.