The internal flow in nozzle and macroscopic spray characteristics of diesel and biodiesel, by employing a validated numerical model and a laser-based Mie-scattering technique, are investigated. The results indicate that both the mass flow rate and the orifice exit average velocity of diesel are larger than those of biodiesel. Also, that diesel consistently produced higher cavitation intensity and turbulence kinetic energy confirms diesel can boost the naissance of cavitation and the turbulence disturbance inside the nozzle. Meanwhile, the cavitation intensity and the turbulence kinetic energy increase dramatically as the injection pressure increases; the cavitation domain is consistent with the domain of high turbulence kinetic energy. Furthermore, the radial velocity of diesel is significantly higher than biodiesel under the same injection pressure, while the radial velocities of both fuels increase as the injection pressure increase. Moreover, the spray tip penetration of biodiesel is longer than that of diesel, while the aerodynamic spray cone angle of biodiesel is narrower that of diesel under the same injection pressure. Higher surface tension and viscosity of biodiesel resulted in smaller cavitation intensity, turbulence kinetic energy and radial velocity at the nozzle exit, which in turn contribute to the narrowing of the aerodynamic spray cone angle. (C) 2017 Elsevier Ltd. All rights reserved.