This study aims to evaluate the effects of Exhaust Gas Recirculation (EGR) on the performance and emission characteristics of a single-cylinder, four-stroke diesel engine fueled with a blend of 70% diesel and 30% biodiesel (B30). The engine was operated at a constant speed of 1500 rpm under varying load conditions, using three fuel configurations: pure diesel (B0), B30 without EGR, and B30 with EGR rates ranging from 0% to 40% in 10% increments. The impact of these fuel EGR combinations on engine performance metrics such as brake thermal efficiency (BTE), exhaust temperature, and emissions including nitrogen oxides (NOx), soot, carbon monoxide (CO), and carbon dioxide (CO₂) was systematically analyzed. The experimental results indicate that B30 combined with EGR can be used effectively under the same operational conditions as diesel. Specifically, BTE decreased by 6% with B30 at 10% EGR, but increased by 7% under the same conditions in a different trial, suggesting sensitivity to combustion parameters. Exhaust gas temperature decreased by 16% at 40% EGR. Notably, NOx and soot emissions were significantly reduced by 68% and 37%, respectively, with B30 at 40% EGR. However, this was accompanied by an increase in CO and CO₂ emissions by 33% and 25%, respectively. These findings confirm that integrating EGR with biodiesel–diesel blends can substantially lower NOx emissions and exhaust temperatures, supporting its potential as a viable strategy for cleaner combustion in diesel engines. However, optimization is necessary to balance emission reductions with efficiency and carbon-related emissions.