In the present study, an effort had been made to use natural zeolite from Tapanuli Utara, North Sumatera as a potential catalyst for biodiesel production. Biodiesel production is usuallythrough transesterification, and a catalyst is employed to improve reaction rate and yield. In this research rice bran oil (RBO) was used as feedstock. The objective of this work was to discover the effectiveness of natural zeolite modified by K 2 CO 3 as catalysts in biodiesel production from RBO. K 2 CO 3/natural zeolite catalyst modification was by impregnation method at various K 2 CO 3 concentrations followed by drying and calcination. Transesterification was conducted at 65 C and 500 rpm. Effect of process variables such as the amount of catalyst, reaction time, and the molar ratio of methanol to RBO was investigated. The maximum yield of 98.18% biodiesel was obtained by using 10: 1 molar ratio of methanol to RBO at a reaction time of 3 hours in the presence of 4 w% catalyst. The obtained biodiesel was then characterized by its density, viscosity and ester content. The biodiesel properties met the Indonesia standard (SNI). The results showed that natural zeolite modified by K 2 CO 3 was suitable as a catalyst in the synthesis of biodiesel through transesterification from RBO.