The present investigation accentuates the impact of Undi biodiesel blended diesel on combustion, performance, and exhaust fume profiles of a single-cylinder, four-stroke diesel engine. Five Undi biodiesel-diesel blends were prepared and tested at four variable loads over a constant speed of 1500 (±10) rpm. The Undi biodiesel incorporation to diesel notably improved the in-cylinder pressure and heat release rate (HRR) of the engine. The higher amount of Undi biodiesel addition enhanced the brake thermal efficiency (BTE) and brake specific energy consumption (BSEC) of the engine. In addition, the Undi biodiesel facilitated the reduction of the major pollutants, such as unburned hydrocarbon (UHC), carbon monoxide, and particulate matter (PM) emissions with slightly higher oxides of nitrogen emissions of the engine. To this end, a trade-off study was introduced to locate the favorable diesel engine operating conditions under Undi biodiesel-diesel strategies. The optimal results of the engine operation were found to be 32.65% of brake thermal efficiency, 1.21 g/kWh of brake specific cumulated oxides of nitrogen and unburned hydrocarbon, 0.94 g/kWh of brake specific carbon monoxide (BSCO), and 0.32 g/kWh of brake specific particulate matter (BSPM) for 50% (by volume) Undi biodiesel blend at 5.6 bar brake mean effective pressure (BMEP) with a relative closeness value of 0.978, which brings up the pertinence of the trade-off study in diesel engine platforms.