Phyllidiella zeylanica exhibits an elongated oval form with longitudinal rows of tubercles that curve to converge at both ends of the body. Its color vary from a muted purple to a slightly more vivid pink-purple, accompanied by intermittent black lines along the body between tubercle rows. The retractable black rhinophores are noticeable in images, and a black longitudinal stripe marks the sole of the foot. While these creatures can reach a length of 12 centimeters, they typically attain smaller sizes.