This study was conducted to ascertain the toxicity effect of Indigofera tinctoria on haematology and oxidative stress biomarker on the liver, kidney, gills, and tissue of Nile tilapia (Oreochromis niloticus) juveniles. Matured leaves of Indigofera tinctoria were collected, dried, and pulverized. Graded levels of the Indigofera tinctoria leaf powder were weighed and dissolved in 250 ml of water. Fish specimens were exposed to sub-acute concentrations of Indigofera tinctoria for 21 days. Significant changes and dose-dependent decreases in red blood cells, packed cell volume, hemoglobin values, and progressive increase in white blood cells were observed in Indigofera tinctoria exposed fish. There was an elevation in the activities of oxidative, in the liver, kidney, gill and tissue of the fish. The present findings show that disposal of leaves, effluent from Indigofera tinctoria should be done with extreme caution as it could threaten the life and existence of the aquatic organism.