Clays and clay-based catalysts have attracted significant attention in recent years due to their extremely useful and versatile catalytic properties. These are considered as one of the best among the viable choices available for green synthetic methods. Montmorillonite (MMT), which is an efficient green catalyst, has been used for many organic syntheses and transformations either directly or in modified forms by incorporating small structural modification. In this study MMT K-10 doped with Ba+2 ions has been used as catalyst in transesterification of Pongamia pinnata Oil for production of biodiesel. The catalyst has been characterized using FTIR and XRD whereas the transesterified product by NMR and GC-MS. The modified catalyst produced good yield at ambient temperature and reduced the chances of saponification of the product. The method involved easy work up compared to the conventional methods which employ alkali catalysts.