This study includes the experimental evaluation of performance, combustion and emission characteristics of cottonseed and grapeseed biodiesels and blends containing bioethanol in a diesel engine with different engine speeds at full load. Addition of bioethanol into the fuels (diesel and biodiesel) used by diesel engines is considered an effective solution. The study observed that the cetane number, viscosity, density and lower heating value of fuel were reduced after the addition of bioethanol in all engine speeds. While the brake power and torque values were reduced as the rate of bioethanol increased, additionally specific fuel consumption, maximum cylinder pressure, heat release and ignition delay also increased. Reviewing the emission results, carbon monoxide (CO) and total hydrocarbon (THC) emissions increased as bioethanol rate increased, nitrogen oxides (NOx) and smoke emissions were reduced.