Utilization of waste cooking oil (WCO) for producing green diesel has attracted considerable attention as an alternative to fossil fuels. Decarboxylation is a promising pathway to convert WCO into green diesel. In this study, decarboxylation of oleic acid (OA) (model compound of WCO) was studied using ScCO2 in a batch reactor at 325 - 400 °C, 8.27 - 9.65 MPa and 1 - 3 h. Up to 98% decarboxylation and 49% liquid fuel yield were obtained using 7.5 wt% MoO3/γ-Al2O3 catalyst at the optimum conditions of feed to catalyst ratio of 10:3 (5 g-OA/1.5 g-cat), 375 °C temperature and 3 h of reaction time without adding any external H2. Analysis of liquid products identified the extent of decarboxylation and the lengths of the hydrocarbon chains of the liquid products. The liquid product formed can easily be blended with conventional diesel or directly used as a green fuel to lower our dependency on fossil fuels. All rights reserved, Elsevier.