Environmental concerns have increased significantly world over in the past decade. Regulatory agencies are becoming increasingly concerned with particulate emissions as the health and environmental effects are getting understood better due to rapid development in instrumentation. Biodiesel is one of the most promising alternative diesel fuels, which is getting global acceptability among the automotive/ engine manufactures as well as users due to numerous benefits it offers over the conventional diesel. While much of literature is available on particulate emitted by diesel fuelled engine, little is known by particulate emissions from biodiesel fuelled compression ignition (CI) engine.This study concentrates on the characterization of particulate emissions from mineral diesel vis-à-vis biodiesel (B100) and its optimum blend (20%, B20) with mineral diesel. The engine exhaust particle sizer (EEPS) was used for size, surface area and mass distributions of particulate emitted by these fuels under varying engine operating conditions. EEPS measures particulate size range from 5.6 nm to 560 nm with a size resolution of 16 channels per decade (a total of 32 channels). A naturally-aspirated, single-cylinder, direct-injection, water-cooled, compression ignition engine was operated at a constant speed of 1500 rpm at different engine loads for the experiment. It was found that number and size distribution of particulate depend on the engine load. The width of the size distribution increased with increasing engine load. The number distribution was found to obey log-normal assumption. Compared with mineral diesel fuel, biodiesel and its blend showed lower particle size, number and mass distribution, indicating towards lower environmental and health impact compared to mineral diesel.