Steam injection technique newly proposed with EGR (exhaust gas recirculation) is applied into a direct injection diesel engine to decrease NOx emissions for the objective of reaching the new emission regulations. Experimental and combustion model as a theoretical methodology has been done. Steam injected diesel engine with EGR has been performed using a combustion model for 20% steam (S20) and 10% EGR (E10) ratios of fuel mass injected per cycle at full-load conditions. The results have been compared with S20 in terms of performance and NO, CO, CO2, and HC emissions. In the experimental results, NO emissions decreased up to 48.3% at the condition of S20 + E10 when compared to S20 with the increase of 3.5% in SFC (specific fuel consumption). As a result, when the small deterioration in the SFC is tolerated, the presented study could be used as an essential tool by the real-engine designers. (C) 2014 Elsevier Ltd. All rights reserved.