2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (BTMLP, CAS No. 125304-04-3) is widely used as a liquid ultraviolet absorber that prevents deterioration of synthetic resins and so on. To investigate its toxicological properties and determine the no-observed-adverse-effect level (NOAEL), a 90-day repeated oral toxicological study of BTMLP was conducted in Crl:CD (SD) rats at doses of 0 (vehicle control, corn oil), 100, 300, and 1000 mg/kg/day. There was no observed mortality or abnormal clinical signs related to the treatment of any group. Body weight and food consumption were not affected by BTMLP treatment. In males, significant prolongations of prothrombin time and activated partial thrombin time were observed in the BTMLP-treated groups. Histopathological examination revealed a slight increase of the eosinophilic bodies and hyaline droplets in the renal cortical tubules in the 1000 mg/kg group in males. As mentioned above, the toxic effect of the BTMLP was noted in the blood coagulation system and kidneys only in males. Based on these findings, the NOAEL was judged to be less than 100 mg/kg/day in males and 1000 mg/kg/day in females under this study’s condition.