The electrochemical behavior of rosmarinic acid at the surface of a DNA-coated electrode was investigated using square-wave stripping voltammetry. The voltammetric studies showed that rosmarinic acid is oxidized in two successive pH-dependent steps each with the transfer of two electrons and two protons. These oxidations correspond to two electroactive catechol groups. Moreover, strong interaction between the immobilized DNA and rosmarinic acid accumulates rosmarinic acid on the electrode surface resulting in an efficient preconcentration leading to high sensitivity of the sensor for rosmarinic acid determination. Several experimental parameters affecting the sensor response were optimized. Under optimized conditions, a linear concentration range of 0.040-1.5 mu M with a detection limit of 0.014 mu M was obtained. The proposed method was successfully applied to the analysis of a rosemary extract. The obtained data was in good agreement to that obtained from HPLC analysis. (C) 2015 The Electrochemical Society. All rights reserved.