Pasipha johnsoni has an elongate body with parallel margins that can reach up to 4 cm in length. The front tip of the body is rounded, while the back tip is pointed. The dorsum is a dark grey color with two black lateral stripes running down the entire dorsal side, with the exception of the cephalicregion, where they are light grey. The color of the dorsal pigment lightens towards the margins. The ventral side of the body is light grey.