Impacts of titanium dioxide nanoparticles (TiO2 NPs) on serum glucose, albumin, total protein, cholesterol, triglyceride, sodium (Na+), potassium (K+), and chloride ion (Cl-) levels and serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and cholinesterase (ChE) activities of Clarias gariepinus were determined after exposing the fish to 1, 5 and 10 mg/L titanium applied as TiO2 over 1, 4 and 7 days. No mortality was observed during the experiments. Serum glucose and albumin levels increased while serum total protein, cholesterol and triglyceride levels decreased compared to control at the end of the 7th day. Serum Na+, K+ and Cl- levels of C. gariepinus decreased after 7 days of exposure to 10 mg/L TiO2 NPs. ChE activity decreased and AST, ALT, ALP activities increased at all exposure concentrations and LDH activities increased compared to control after 4 and 7 days of exposure to TiO2 NPs in C. gariepinus.