The lethal concentration and histopathological damages of crude oil water soluble fractions (WSFs) on the liver and gills damages of the Red Tilapia (Oreochromis niloticus) was investigated. Water soluble fractions of the crude oil was prepared according to Anderson et al. method and was made into five concentrations; Toxicity of WSFs on Red Tilapia was investigated at 0 ppm control, 5 ppm, 6 ppm, 8 ppm and 10 ppm. The dilutions were made with the control water (habitat of which fish were cultured). Twenty fish per group (8.5± 1.5g) were exposed to 5 liter each of the five concentrations levels of the WSFs and the fishes were observed for 96 hours. Water quality parameters were determined and showed that salinity was 34 ppt, pH was 7.5, dissolved oxygen (DO) was 12 mg/l and temperature was 28°C. The number of dead fishes per group was recorded against the time of their death. The obtained data were used to determine the median lethal concentration (LC50) of the WSFs of the crude oil using arithmetic method