The haematological variations in Sarotherodon melanotheron exposed to sub lethal concentrations of linear akyl benzene sulfonate based detergent were investigated. One hundrerd and fifty adult sizes of S. melanotheron (mean length 10cm + 1.99 SD and mean weight 105.11g+8.33 SD) were exposed to different concentrations. (0.00, 0.50, 1.00, 1.50 and 2.50 mg/L) of alkyl benzene sulfonate for 15 days. The study assessed the effect of exposure to detergent on some haenatological parameters which include Haemoglobin (Hb) , Red blood cell (RBC), packed cell volume (PCV), white blood cell (WBC), leucocrit, thrombocytes, neutrophils, lymptocytes, monocytes, mean corpuscular haemoglobin concentration (MCHC), mean corpuscular volume (MCV) and oxygen carrying capacity (OCC). The results obtained indicated a significant (P<0.05) reduction in the values of Hb, RBC, PCV, leucocrit, thrombocytes, lymphocytes, MCHC, and OCC, with increasing concentrations of the contaminants. However, exposure of S. melanotheron  to alkyl benzene, caused significant (P<0.05) elevation in the values of WBC, neutrophils, monocytes, MCV and MCH when compared to the control values. Exposure of this specie to sub lethal levels of detergents distorted various mechanisms of its haematological variables, which may result in irregular metabolism of the fish. Consequently, there is need for proper disposal of domestic wastes containing detergent into the aquatic environment.