The current study employs a range of pilot fuel injection pressures (500 bar, 600 bar, and 700 bar) strategies on a common rail direct injection diesel engine supplemented with a constant hydrogen flow rate. The parameters such as engine speed (1900 RPM), CR (16.5), and pilot fuel, i.e., diesel injection timing (15°BTDC), were kept constant while keeping variable load conditions (10 Nm, 20 Nm, and 30 Nm). Neat diesel fuel and diesel fuel with 15% hydrogen enrichment were chosen as test fuels for the study. Hydrogen addition to baseline diesel fuel, as well as higher pressure of diesel fuel injection, has positively impacted the important indicators of the test engine. Under optimum test conditions (Load: 30 Nm, Fuel blend: Diesel+15% H2, and FIP: 700 bar), performance indices, i.e., BTE, BSFC, and BSEC, showed considerable improvement. At 700 bar and 15% hydrogen supplementation, BTE, BSFC, and BSEC were observed as 20.36%, 315.14 g/kWh and 176.82 kJ/kWh as opposed to 9.58%, 561.5 g/kWh and 375.78 kJ/kWh for neat diesel. The highest in-cylinder pressure of 80.19 bar was recorded for 700 bar pilot FIP and 30 Nm load for hydrogen-blended diesel fuel. Ignition delay and combustion duration also experienced a significant decline with the cumulative effect of higher pilot FIP, load conditions, and hydrogen enrichment effects. Trade-off was experienced in engine exhaust characteristics between NOx and CO emissions on account of input factors (i.e., load, fuel blending, and FIP), with the highest NOx emissions of 1063 PPM and CO emissions of 92 PPM under optimum test conditions. Higher FIP (700 bar) and hydrogen supplementation have led to a significant rise in NOx levels to 1063 PPM as compared to 782 PPM for neat diesel at FIP 500 bar.