Present research work shows the emissions and flame analysis of oxy‐fuel combustion of diesel and diesel/biodiesel blends in the experimental test burner manufactured in Mechanical power engineering laboratory at Tanta University, Egypt. Diesel and a mixture of diesel and biodiesel (B0, B10, B20, B30, and B40) used as a fuel with the effect of pure air and oxy‐combustion. Different emission parameters (carbon monoxide, carbon dioxide, unburned hydrocarbons, NOx, and soot opacity) and the flame parameters (flame cone angle and flame length) were also studied. It has been found that the emission parameters and the flame temperature are higher in diesel fuel than diesel and biodiesel blends for pure air combustion and oxy‐combustion. It has also been found that flame parameters (the flame cone angle and flame penetration length) decreased by adding the oxygen into the charged air and increased by increasing the biodiesel mass percentage. The complete combustion of the fuel blends will dramatically increase the flame temperature due to the presence of a sufficient amount of oxygen for the early chemical reaction between fuel and oxidizer. These results indicated that the biodiesel could be the best alternative as well as an environmentally friendly fuel for diesel engines.