The present experimental work focuses on studying the influence of 25 ppm zirconium oxide (Zr2O3) nano additives in B20 spirulina microalgae biodiesel blend (20% spirulina microalgae biodiesel + 80% diesel fuel). For testing, B20, B20+Zr and mineral diesel were considered and performance, combustion and emission characteristics were studied. Experimental results revealed that, on fuelling B20 blend with Zr2O3 nano additives, BSEC is lowered by 4.87%, BTE is improved by 7.92%, CO, HC, Smoke and NOx emissions were reduced by 11.32%, 5.73%, 6.56% and 9.42% respectively. Further, Zr2O3 nano additives in B20 resulted in improved pressure, and HRR of 72.68 bar, and 66.37 J/°CA which are marginally high in comparison with diesel and B20.