In the present study, new host and locality records of Cucullanus aliyaii Akhtar and Mujib (2012), a cuculanid nematode isolated from the intestine of the rabbitfish, Siganus canaliculatus collected from the Red Sea, coasts of Hurghada city, Egypt during the period from January to September 2017. Fifteen out of 55 (27.3%) of the examined fish were infected. Worms were recorded by naked eyes on the flesh, stomach, intestines, as well as body cavities of the infected fish. Light and scanning electron microscopy revealed that the isolated worms possessed the important criteria characteristic for members of family Cuculanidae: dimensions of oesophagus, spicules, mucron, size of pseudobuccal capsule, eggs, the position of deirids, excretory pore and vulva, numbers and arrangement of caudal papillae, host groups and zoogeographical regions. The recorded parasite was whitish and small-sized, female worms were 9.40±2 (7.4-10.3) x 2.5±0.2 (2.00-2.60) mm while male worms were 6.30±0.02 (6.00-8.30) mm x 1.60±0.02 (1.59-1.73) mm. Oral aperture was dorsoventrally elongate, slit-like, surrounded by distinct collarette, beared one row of small denticles on its inner surface; four submedian cephalic papillae and a pair of prominent lateral amphids present. Oesophagus was of two distinct portions: anterior pseudobuccal capsule measured 0.50±0.02 (0.47-0.053) mm in length, narrowing immediately below nerve ring; and posterior with a club-shaped muscular structure measured 0.45±0.02 (0.41-0.49) mm in length