Volatile organic compounds (VOCs), a group of environmental pollutants, are emitted in large quantities when fossil fuel is burned in automobiles. This research investigates the VOCs in the exhaust emissions from a common rail diesel engine fueled with canola oil biodiesel fuel (COBF), conventional diesel fuel (CDF), and B20 (20% COBF blended with 80% CDF by volume) at various engine loads (30 Nm, 80 Nm, 130 Nm) and a constant engine speed of 1500 rpm. The results indicate that the regulated emissions (CO, HC, PM) were reduced obviously when COBF and B20 were used in a CRDI diesel engine, and a larger number of VOCs (about 30 types) are emitted with CDF and the quantity emitted is greater than with B20 and COBF. The total VOC emissions (TVOC) of B20 were lower than those with the other test fuels at all experimental conditions. In addition, this paper presents a simple approach for sampling VOC emissions from diesel engines, uses a gas chromatography/mass spectrometry (GC/MS) analysis, and also confirms that COBF blended with CDF in a volume fraction of 20-80 is an excellent alternative fuel based on VOC emissions.