A common defective phenomenon in abrasive waterjet (AWJ) cutting of layered materials such as polymer matrix composites is delamination which occurs only when the jet is unable to cut through the workpiece. It is therefore essential to predict the depth of penetration in order to achieve through cuts and to eliminate delamination. A semi-empirical model is developed for predicting the depth of jet penetration in AWJ cutting of polymer matrix composites. The plausibility of the model is then assessed by analysing the predicted trends of this performance measure and by comparing with the experimental results. It is shown that the model gives adequate predictions and can be used for process planning.