The main objective of this research work is to investigate the effect of multiwalled carbon nanotubes and cerium oxide nano-additives in lemon and orange peel oil biofuel blends in compression ignition engine. Eight different blends are prepared using lemon and orange peel oil in 20% volume ratio with diesel in which nanoparticles are added at two concentrations (50 and 100 ppm). The study revealed that brake thermal efficiency of carbon nanoparticle and cerium oxide addition with biofuels is marginally lower then diesel fuel. Furthermore, brake specific energy consumption for biofuel samples with and without nanoparticles are substantially lower than diesel fuel and in particular, the 50 ppm cerium oxide with lemon peel oil blend has resulted in 16.4% reduction in brake specific energy consumption. The Carbon nanotubes and cerium oxide in orange oil exhibit higher heat release rate high in-cylinder pressure than other fuel respectively. Moreover, the cerium oxide in orange oil at 50 ppm concentration has resulted in 53.8% reduction in carbon monoxide emission and similar kind of reduction is also observed in hydrocarbon emission as well. On the other hand, the nanoparticles addition with lemon peel and orange peel at all concentrations has shown only marginal reduction in NOx emission. © 2019 Elsevier Ltd