Sub-chronic exposure of Tilapia (Oreochromis mosambicus) to Anabeanopsis abijatae, a toxic cyanobacterium was investigated with emphasis on the biochemical indices and histopathology (liver and gill). A single dose of two different concentrations (100μg/kg and 200μg/kg) of extracted toxins were intraperitoneally injected in Tilapia. Serum biochemical assays with commercial kits (Liquid Gold reagents) indicated that the levels of glucose, cholesterol, bilirubin, triglycerides and the activities of alanine aminotransferase (ALT), alkaline phosphatase (ALP) and aspartate aminotransferase (AST) were significantly increased as compared to the control levels. Histopathology of liver revealed congestion of parenchymatic cells with hepatic necrosis and vacuolation of cartilage with inflammatory cell infiltration was observed in gills.