Background: Fullerenes are nanoparticles composed fully of carbon molecule that are widely used in industry, mostly cosmetics and also play an important role as antioxidants. Aim: The present study was aimed to evaluate the consequence of fullerene toxicity on oxygen consumption and behavioural modification in cichlid fish, Etroplus maculatus. Methods: Fishes were exposed at 100 __ampersandsignmu;g/ L concentration of fullerene through fish feed for 96 h. Body weight of the animals, weights of gill, liver, brain and gonads along with mucous deposition was observed. Oxygen consumption of control and treatment groups was evaluated. Behavioural modification of fishes after exposure to fullerene was recorded throughout the study. Result: Oxygen consumption was decreased at the end of treatment. Weights of fish were decreased and there was significant increase in mucous deposition throughout the body of treated animal. Weights of gill, liver, brain, ovary and testis decreased significantly than that of control fish. Alterations in behavioural patterns including erratic swimming and surfacing activity, slow opercular movements, reddening of skin and haemorrhage through surface of the body were well marked during the period of trial. However, no mortality was observed throughout the study. Conclusion: The present study accordingly reveals that fullerene induced alteration on oxygen consumption and behaviour in fish.