Dwindling petroleum products and environment degradation, owing to the gases from the exhaust tailpipe of compression ignition engines, have obligated the investigators to invent some unconventional fuel. Current experimentation aimed to evaluate the combustion, performance and emission characteristics of a dual fuel engine by using blends of diesel and n-butanol as pilot fuel with biogas as primary fuel. Under dual fuel mode, biogas at different mass flow rates (0.5, 1.2 and 2.0 kg h−1) was admitted into the engine through inlet manifold and blends of n-butanol with diesel (D90/nb10 and D80/nb20) were injected as a pilot fuel to initiate the combustion. The fuel properties of the tested fuels were measured as per ASTM standards. The engine testing was carried out at constant speed of 1500 rpm and different engine loads. The experimental results depict that under dual fuel mode, brake-specific fuel consumption increased by 22.6% and brake thermal efficiency of the engine decreased by 11.9% in comparison to conventional diesel. As far as emissions are concerned, carbon monoxide and hydrocarbon emissions increased by 50.8 and 11.9%, respectively, whereas NOx and smoke opacity decreased by 19.8 and 40.9%, respectively, when compared to conventional diesel. Thus, such fuel combinations can be used in existing diesel engines for addressing long term energy needs and solving environmental associated challenges.