The study investigated the acute toxicity of 2, 3-dicholrovinyl dimethyl phosphate (Sniper 1000EC) on the African mud catfish, Clarias gariepinus juveniles (mean weight 19.47 ~c 1.05g) using static bioassay method. Sniper 1000EC is an organophosphate pesticide. Each treatment in the acute test was in triplicate with bioassay media concentration of 0,5, 10, 15 and 20 mg/l. Data on mortalities of fish, water physic-chemical parameters as well as changes in haematological indices were subjected to one way analysis of variance (ANOVA) at 5% probability level. Duncan multiple range test was used to separate differences between the means. The 96hr LC50 estimated by probit analysis during the exposure was found to be 8.20mg/l. Behavioural abnormalities of the exposed fish included erratic and uncoordinated swimming and bleached skin with lesion at the highest concentration (20mg/l). Blood dyscrasias attributable to the toxicant was observed with a significant (p<0.05) decrease in haemoglobin, haematocrit, red blood cells, white blood cells, lymphocytes and monocytes. Mean corpuscular volume (MCV), Mean corpuscular haemoglobin (MCH), neutrophils, eosinophil and basophil increased significantly (p<0.05) with increasing concentrations of the toxicant. These abnormalities in body and blood parameters as a result of exposure to the toxicant make the study to recommend that the use of Sniper 1000EC by local fishermen be banned to preserve aquatic lives in Nigerian inland water bodies