Nanoparticles (NPs) are now being used in many industrial activities, such as mining, paint and glass industries. The frequent industrial use of NPs contributes to environmental pollution and may cause cellular and oxidative damage in native organisms. In this study, the toxic effects of titanium dioxide nanoparticles (TiO2 NPs) were investigated using Galleria mellonella larvae as a model insect species. Alterations in cell damage indicators, such as alanine transferase, aspartate transferase, lactate dehydrogenase, non-enzymatic antioxidants and biochemical parameters, were determined in the hemolymph of G. mellonella larvae exposed to TiO2 NPs at different concentrations (5, 50, 250 and 1250 mu g/mL) in their diets. TiO2 NPs caused concentration-dependent cellular damage in the hemolymph of G. mellonella larvae and increased the levels of the non-enzymatic antioxidants uric acid and bilirubin. In addition, total protein in hemolymph significantly decreased at the highest concentration (1250 mu g/mL) of TiO2 NPs. Level of the urea increased at the highest concentration (1250 mu g/mL) of TiO2 NPs, whereas the amount of glucose was not affected. These findings demonstrated that TiO2 NPs caused concentration-dependent toxic effects on G. mellonella larvae.