Using biogas in IC engines takes a toll on the engine performance due to low volumetric efficiency of the dual-fuel mode and low energy density of biogas, however, some engine modifications can be employed to compensate for this loss in performance. The purpose of this study is to investigate the effect of intake air pressure on the engine characteristics of a dual-fuel engine running on biogas and diesel. A single-cylinder four-stroke CI engine is used in dual-fuel mode to perform the tests at different biogas flow rates and different engine loads. A single-stage reciprocating compressor is used to serve as a supercharger to provide air at different pressures to the intake manifold. The results show that the brake thermal efficiency improves by around 2%, and the brake specific energy consumption reduces by 1–4.5% on increasing the intake air pressure. The HC and CO emissions are observed to decrease by around 12% and 15%, respectively. However, very high intake pressures are shown to have less improvement in the HC emissions. There is an increase in the NOx emissions of around 35% with the increase in intake air pressure, however, high air pressures reduce this increase by an amount of around 7%. © 2020, © 2020 Taylor & Francis Group, LLC.