Based on light and scanning electron microscopy, a Cucullanus species (Nematoda: Cucullanidae Railliet and Henry, 1915) was isolated from the intestine of the commercially important marine fish Mulloidichthys flavolineatus (Perciformes: Mullidae) from Hurghada, Egypt, as a new host and locality record. Cucullanus cirratus Müller, 1777 is primarily characterized by the dorsoventral oral opening, surrounded by narrow membranous alae (collarette) supported by a row of numerous minute teeth, four submedian cephalic papillae, a pair of small lateral amphids, and a funnel-shaped pseudobuccal capsule. The excretory pore is located at the level of the posterior half of the esophagus between the nerve ring and the intestine. The intestine is simple and without cecum. Males show unequal caudal spicules, with the left spicule measuring 1.20–1.41 mm and the right spicule measuring 0.644–0.736 mm. There are 10 pairs of caudal papillae, including five preclocal and five postclocal pairs as well as a pair of small phasmids. The tail is simple and conical in both sexes.