Titanium dioxide nanoparticles (nTiO ) have raised environmental concerns and display potential hazards to aquatic organisms and even humans. However, only a few reports tested the toxicity of nTiO to rotifers. In the present study, acute and chronic toxicity of nTiO to the freshwater rotifer Brachionus calyciflorus was investigated at different temperatures. At 25°C, the 24 and 48-hr LC was 117.14 and 60.11 mg/L, respectively. At 15°C, 20°C, 25°C, and 30°C, exposure to nTiO significantly decreased life expectancy at birth, net reproductive rate, generation time, average lifespan, and/or intrinsic rate of population increase of B. calyciflorus (p < .05). High temperature enhanced the toxicity of nTiO to rotifers. The swimming linear speed of rotifers significantly increased (p < .05) in treatments with 200 µg/L nTiO , compared with the control. In addition, treatments with 8 µg/L to 5 mg/L nTiO significantly increased superoxide dismutase activity (p < .05). Glutathione content and catalase activity increased significantly after exposure to 8 µg/L nTiO  but decreased significantly in treatments with nTiO concentrations ranging from 40 µg/L to 5 mg/L (p < .05). There were no significant changes in malondialdehyde contents among nTiO treatments and control. Overall, the present study indicated that nTiO revealed high toxicity to rotifers, displaying high environmental risks to aquatic ecosystems.