In this study, the removal of oleic acid from laboratory prepared oleic acid-sunflower oil mixtures has been investigated using Amberlyst A26 (OH) ion exchange resin. The influence of experimental conditions such as contact time, temperature, adsorbent amount and initial concentration of oleic acid was studied. The "pseudo-first order and pseudo-second order" kinetic models and "Langmuir and Freundlich" isotherms have been used to analyze obtained experimental results. It was observed that adsorption of oleic acid on resin follows the pseudo-second order kinetic model and both isotherm models were found to be appropriate to describe adsorption of oleic acid on Amberlyst A26 (OH) from sunflower oil. After the oleic acid content was decreased to 0.2% via adsorption, transesterification performances of oleic acid-sunflower oil mixtures increased and reached to biodiesel yield of 94% which was also obtained with fresh sunflower oil under the same reaction conditions. (C) 2013 Elsevier B.V. All rights reserved.