ABSTRACT Objectives The prevalence and impact of the branchiuran copepod parasite Argulus japonicus on the snakehead fish Channa punctata were investigated in the southwestern region of Bangladesh. Methods Parasitic infestation was examined to determine parasitological indexes including prevalence (%), mean intensity (MI), abundance (A), and index of infestation (IOI). Haematological parameters were also determined, along with morphological identification, clinical signs, and size grading of A. japonicus . In addition, histological alterations in the liver, kidneys, gills, and skin of C. punctata were examined. Results Among 140 C. punctata individuals, 85 were found to be infested with a total of 245 A. japonicus parasites. Most of the parasites were located on the gill surfaces, around the eyes, and on the external parts of the body. The main physical features of A. japonicus were identified and documented during the observations. The haematological parameters showed variation across different experimental sites, and several clinical signs of infestation were observed. Four treatment methods for the elimination of A. japonicus were tested. Heat treatment (T 3 ) was found to be the most effective method of the four. Conclusion This study highlights the serious health problems caused by A. japonicus infestation in C. punctata in southwestern Bangladesh.