In the present work, biodiesel has been produced from waste chicken fat, and its usability test as an alternative fuel has been comprehensively discussed. A diesel engine has been tested at varying engine speeds (from 1800 to 3400 prm with the interval of 400 rpm) under full load condition. Esterification and transesterification of waste chicken fat were used to produce chicken methyl ester. Then this produced biodiesel has been blended into the conventional diesel fuel volumetrically from 25 to 100 %, and the main properties of these test fuels have been determined. In the results, it is noticed that the addition of waste chicken biodiesel to petroleum diesel fuel declines the engine brake power and thermal efficiency by 28 and 23 % due to the low calorific value, and high viscosity of biodiesel, but increases the EGT and BSFC by 29 and 25 %, respectively. Thanks to the high oxygen content of biodiesel fuel, hydrocarbons, carbon monoxide, and smoke concentrations have been dropped by approximately 47, 12, and 48 %, respectively but the concentration of nitrogen oxides has shown an increment to be 25 % when chicken methyl esters (B100) have been completely used instead of diesel fuel. On the other hand, significant combustion parameters such as heat release rate, ignition delay, and peak in-cylinder pressure have been recorded less than those of methyl ester by 8, 10, and 19 %, respectively as compared to those of conventional diesel fuel. Multi-criteria decision-making with grey relational analysis has been also conducted in this work. Based on the optimization results, The blending ratio range between 0 and 20 % and the speed range between 2600 and 3000 rpm is recommended because of the improvement in engine combustion and emission characteristics. In the conclusion, the present work reported that the waste chicken methyl ester can be utilized as a substitute fuel at the modest blending ratios for diesel engines without any modification on the vehicular system.