With increasing pollution concerns and stringent emission regulations, it has become difficult to meet the emission standards with the use of a single fuel. Binary and ternary fuel mixtures are being investigated all over the globe to satisfy the emission norms. In the present work, a reduced reaction mechanism for a waste cooking oil (WCO) biodiesel/n-pentanol mixture is proposed for the chemical kinetic simulation of an internal combustion engine. The mechanism consists of 146 species and 506 reactions. WCO biodiesel and n-pentanol are biofuels with many advantages. WCO biodiesel has properties (cetane number, viscosity, etc.) that are similar to those of diesel fuel, whereas n-pentanol has a high boiling temperature, low heat of vaporization, high lower heating value, and low autoignition temperature compared to other shorter chain alcohols. Mixing of higher molecular weight alcohols (n-pentanol) with diesel/biodiesel lowers the knock resistance as a result of their high reactivity at low as well as high temperatures. This characteristic makes them suitable for a diesel engine and advanced engine combustion modes, such as homogeneous charge compression ignition and reactivity controlled compression ignition engines.