Cucullanus sp. is a genus of nematode infecting Barbonymus schwanenfeldii. It is categorized under Family Cucullunidae. The genus Cucullanus sp consists of various species around the world, parasitizing freshwater, brackish-water or marine fishes. Cucullanus sp are mainly found in internal organs like stomach, intestine, kidney, and spleen. This parasitic organism can cause an economic impact, especially for animals with high market value, which are commercialized and used for human consumption. The objectives of this study are to study the morphological characteristics of Cucullanus sp and to identify genus of Cucullanus sp which are found on tinfoil barb, Barbonymus schwanenfeldii at Kenyir Lake, Terengganu. There is not enough data on Cucullanus sp on B. schwanenfeldii. Six samples of tinfoil barb were collected at Kenyir Lake from 25 to 27 October 2018. Each sample of fish was measured and recorded for length and weight using ruler and weighing balance respectively. The fish were examined at camping site at Lawit Resort, Kenyir Lake. The nematode species found were brought back to Health of Aquatic Organism laboratory. The abdominal and gastrointestinal tracts of the fishes were dissected and placed in petri dishes. The nematodes found were collected and observed under the dissecting microscope. The nematode specimen was placed on a glass slide with a drop of lactophenol and observed under the compound microscope fitted with dino-eye. The sample was later fixed with 70% alcohol. The morphological characteristic was drawn using camera lucida fitted to a compound microscope. (40X magnification). The picture of nematode was captured by using Advanced Research Microscope (Nikon Eclipse 80i) and measurements of the nematode was also made. Hence, the nematode found was identified as male Cucullanus sp.