For the present study, azo dye tartrazine (acid yellow 23) having wide range of application in textiles and synthetic foods, was used to assess the toxic effects and biomarker responses in fish Labeo rohita (Hamilton, 1822), commonly known as rohu. In toxicity studies haematological estimation is recognized as significant before many years. Acute (T1, T2 and T3 for 96 hours) and chronic (CT1 and CT2 for 75 days) bioassays were conducted. Major physico-chemical characteristics of aquaria water were analysed and recorded in regular intervals of experiment. After the experimental period, blood was collected and major haematological parameters; Hb, TC, RBC, PCV, MCV, MCH and MCHC were analysed. The results show that parameters Hb, RBC, PCV, MCV, MCH were significantly reduced and TC was significantly increased in highest concentration of acute test (T3) and in chronic tests (CT1 and CT2). The changes in haematological parameters can reflect the physiological status of animal and indicates the environmental conditions where they being. The experimental study establishes that haematological indices such as Hb, TC, RBC, PCV, MCV, and MCH are good biomarkers of the tartrazine exposure in fishes..