The long-term use of tenofovir, a commonly used anti-HIV drug, can result in renal damage. The mechanism of tenofovir disoproxil fumarate (TDF) nephrotoxicity is not clear, although it has been shown to target proximal tubular mitochondria. In the present study, the effects of chronic TDF treatment on the proximal tubular function, renal mitochondrial function, and the activities of the electron transport chain (ETC) complexes were studied in rats. Damage to proximal tubular mitochondria and proximal tubular dysfunction was observed. The impaired mitochondrial function such as the respiratory control ratio, 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT) reduction, and mitochondrial swelling was observed. The activities of the electron chain complexes I, II, IV, and V were decreased by 46%, 20%, 26%, and 21%, respectively, in the TDF-treated rat kidneys. It is suggested that TDF induced proximal tubular mitochondrial dysfunction and ETC defects may impair ATP production, resulting in proximal tubular damage and dysfunction. © 2014 Wiley Periodicals, Inc.