This study aims to investigate the effect of hydrogen injection on the performance and emissions of a compression ignition (CI) engine running on biodiesel. The tests are performed on a single-cylinder CI engine cooled by water, operating at a consistent speed of 1500 rpm. The torque load range varies from 0.01 kg to 18 kg, and hydrogen injection rates range from 4 litres per minute (lpm) to 10 lpm. The study focuses on evaluating the impact of hydrogen injection on various performance metrics, including exergetic efficiency, brake thermal efficiency, brake specific fuel consumption (BSFC), cylinder pressure, heat release rate, and exhaust gas temperature. The findings reveal that hydrogen injection significantly improves the performance of the biodiesel-run CI engine. The highest improvement is observed at a hydrogen injection rate of 10 lpm, which results in a 5% decrease in BSFC, a 6% increase in brake thermal efficiency, and an exergetic efficiency of 25.3%. Furthermore, exergy analysis is conducted to assess the contribution of different components, such as shaft work, cooling water, exhaust gas availability, and entropy generation. The results demonstrate that hydrogen injection can be an effective strategy for enhancing the performance and sustainability of CI engines powered by biodiesel. Overall, this research provides information about the potential advantages of hydrogen injection for CI engines powered by biodiesel. The findings of this study will be useful for future investigations and creation of sustainable engine technologies.