In this paper, the effect of the injector geometry has been investigated on ‎characteristics of the internal nozzle flow and the cavitation phenomenon. To ‎this end, the cavitational flow inside a multi-hole diesel injector was simulated ‎using the computational fluid dynamics. The flow inside the nozzle was ‎considered transient and biphasic (liquid phase and vapor phase) and was ‎simulated using the Eulerian two-fluid model, which is a non-homogeneous ‎model. In this model, governing equations were solved for each phase ‎separately. The interaction between phases was modeled using relevant ‎interfacial exchange terms. To investigate the effect of the nozzle geometry on ‎the cavitational flow, the number of injector holes was varied from 2 to 8. ‎Results showed that by increasing the number of nozzle holes, the structure ‎and the intensity of the vortex flow in the nozzle sac and holes are extremely ‎varied. From the nozzle flow characteristics point of view, an increase in the ‎number of nozzle holes, resulted in a reduction in the injection velocity and the ‎mass flow rate and an increase in the cavitation intensity. Furthermore, the ‎discharge coefficient and the effective area of the nozzle fall with increasing the ‎number of nozzle holes. The simulation method was validated by comparing ‎numerical results with experimental data and a good agreement was achieved.‎