Alcohol is being considered as an alternative to traditional fuels for compression ignition engines due to their oxygen content and biomass origin. Although alcohol generally has lower cetane numbers, which makes them more favorable for premixed combustion, they also offer potential for lowering emissions in internal combustion engines, particularly when combined with strategies such as exhaust gas recirculation (EGR). This research focuses on enhancing the performance of a single-cylinder, four- stroke diesel engine by introducing ethanol into the intake port during the intake phase. Diesel and rubber seed biodiesel were used as primary fuels and were directly injected into the combustion chamber. The findings indicated that adding ethanol to rubber seed biodiesel, along with 10% EGR, led to improved brake thermal efficiency and a reduction in NOX emissions. The ethanol injection timing and duration were optimized for effective dual-fuel operation. At full engine load, the highest brake thermal efficiency recorded with a 20% ethanol energy share was 34% for diesel, 31.16% for B20 with EGR, and 31.15% for B20 without EGR. Furthermore, NOX emissions were reduced by 25.44% and 26.08% for B10 with EGR and B20 with EGR, respectively, at peak thermal efficiency. On the downside, increasing ethanol contribution raised HC, CO₂, and smoke emissions across all loads for both B10 and B20 with EGR. Additionally, B10 and B20 with EGR experienced higher peak cylinder pressures and maximum rate of pressure rise, while ethanol uses also resulted in shorter combustion duration and increased heat release rates.