This paper reports on the development and evaluation of an SPH (Smoothed Particle Hydrodynamics) model for high pressure water flow through and from a nozzle and prediction of its break up into a spray of high speed water droplets. This appears to be the first application of the SPH technique to fully model a high pressure nozzle. The model predicts the internal flow and pressure distribution and enables exploration of the role of the internal geometric insert used in this design of the nozzle. It also predicts exit velocities from the nozzle as well as the pressure distribution generated by the nozzle and droplet size distribution of the resulting spray. Three different nozzle inflow rates were simulated and for all cases the numerical simulation of nozzle and spray gave generally good agreement with experiments, but complete agreement was not achieved. For better agreement, higher resolution for the SPH solution is required. The SPH simulations also show the role that the insert in the nozzle has on the flow and the resulting jet. It produces a flat inclined high velocity liquid jet within the second half of the nozzle which will generate turbulent eddies that may enhance the nucleation of the droplets in the fragmenting jet after it exits the nozzle. Overall, SPH has been shown to have a very good capacity to model high pressure nozzles and with further refinements of the technique should be able to yield accurate, quantitative data. Crown Copyright (C) 2017 Published by Elsevier Ltd. All rights reserved.