Hydrogen is expected to be one of the most important fuel in the near future to solve greenhouse problem and to save conventional fuels. In this study, a Direct Injection (DI) diesel engine was tested for its performance and emissions in dual-fuel (Hydrogen-Diesel) mode operation. Hydrogen was injected into the intake port along with air, while diesel was injected directly inside the cylinder. Hydrogen injection timing and injection duration were varied for a wider range with constant injection timing of 23° Before Injection Top Dead Centre (BITDC) for diesel fuel. When hydrogen is used as a fuel along with diesel, emissions of Hydro Carbon (HC), Carbon monoxide (CO) and Oxides of Nitrogen (NOX) decrease without exhausting more amount of smoke. The maximum brake thermal efficiency obtained is about 30 % at full load for the optimized injection timing of 5° After Gas Exchange Top Dead Centre (AGTDC) and for an injection duration of 90° crank angle. The NOX emission tends to reduce to a lower value of 888 parts per million (ppm) at full load condition for the optimized injection timing of 5° AGTDC and with an injection duration of 90° compared to neat diesel fuel operation.