The effect of sub lethal concentrations of fresh root bark extracts of Plumbago zeylanica on blood compositions of Clarias gariepinus was investigated under static water renewal bioassay during a 21-day exposure period. Concentrations of Plumbago zeylanica extracts used were 0 (control), 26, 39 and 59 mgl-1. The exposure led to anaemic response in fish, this was observed to be time and dose dependent. There were significant decreases in haematological values of PCV (20.66 ± 2.84), Haemoglobin (6.73 ± 0.87), RBC (1.70 ± 0.02), MCV (32.67 ± 0.33), MCHC (38.67 ± 4.33), and MCH (119.67 ± 14.84) at 59 mgl-1. While slight increase was observed in WBC (16016.67 ± 1717. 63) at 39 mgl-1. The muscle/flesh of the exposed fish showed goblet cell hyperplasia, muscle necrosis and calcification at lower concentrations of exposure for both the short term and long term exposure, but disappears at higher concentrations after one week withdrawal without bioaccumulation in the Organs and Tissues. The changes observed indicates that haematological indices could be used as risk assessment tools in aquatic environmental monitoring to assess physiological status of fish exposed to sub lethal effect of toxicants.