Masticophis lateralis is 90–120 centimetres (3.0–3.9 ft) in total length (including tail).

It is slender, with a yellowish stripe along each side, set against a dark brown or black back.

[3] The California whipsnake is known to eat a variety of live animals including insects, lizards, snakes, birds, and small mammals.

[3][4] It shows a strong preference for lizards, which are captured by a grasp of the mouth,[4] and swallowed alive.

As with many species and subspecies, taxonomic reclassification is an ongoing process, and differing sources often disagree.