Lipid-soluble endogenous antioxidants, such as tocopherols, protect biological structures from oxidative damage through their chain-breaking ability and thus the development of a simple method for tocopherol determination is important. In this study, a novel optical sensor-based method was proposed for determining total tocopherol content (TTC) of serum, with selectivity for alpha-tocopherol over beta-carotene. The proposed method is based on the use of a copper(II)-neocuproine complex (Cu(II)-Nc) reagent immobilized onto a Nafion membrane, and the absorbance changes associated with the formation of Cu(I)-Nc chelate on the membrane strip as a result of reaction with serum tocopherols were measured at 450 nm. The calibration graph of a-tocopherol was linear with a slope of 1.96 x 10(4) L mol(-1) cm(-1). The limit of detection and limit of quantification for tocopherol in the proposed method were found as 0.50 and 1.67 mu M, respectively. The TTC value of synthetic serum samples was determined with the use of the proposed method, and the obtained results were comparable to those of the CUPRAC spectrophotometric method. The proposed method enables simple, rapid, and in situ determination of total tocopherol content of serum by taking advantage of optical sensors.