The present paper presents an experimental investigation to explore the impact of burning a blend of biodiesel/jet A-1 fuel in a gas turbine combustion chamber on the flame characteristics and exhaust emissions. The biodiesel portion of the fuel is produced from waste cooking oil by the transesterification method where ultrasonic was used to improve the production process. The B20 blend (20 % vol. biodiesel with Jet A-1) is pre-vaporized and premixed with air prior to its admission to a cylindrical combustion chamber having an inner diameter (D = 0.15 m) and length (L = 0.5 m) via a high swirl burner having a swirl number (SN=0.55). The temperature of the premixed fuel/air mixture entering the combustion chamber is kept constant at 250 °C with an equivalence ratio φ = 0.75 (lean conditions) for all tested cases. The results showed that the use of the B20 blend in comparison with the pure jet-A1 gave slightly lower mean values of gas temperature within the flame region and a significant decline of the levels of exhaust emissions (by about 70% for CO and 58% for NOx). These findings encourage the use of a 20% blend of biodiesel and Jet-A1 fuels in gas turbines without modifications in the combustor design.