Continuous fiber bundles, pre-impregnated with dry polymer fibers by a typical co-mingling technique, were used to prepare unidirectional composite plates. After finding the relevant conditions for full impregnation during thermal treatment, the conditions of the latter were varied so that various morphologies of the semicrystalline thermoplastic matrix could be established between the fibers. The resulting mesostructures in the final composite plates consisted of resin-rich and fiber-rich areas which had a different influence on the interlaminar fracture (ILF) behavior of the composites. For the same mesostructural appearance, the degree of crystallinity could be modified by a separate annealing procedure. It turned out that the local fracture mechanisms were influenced by the particular morphology in the resin-rich regions (fine spherulitic in comparison to coarse spherulitic, under additional influence of local voids). The ILF studies were carried out under mode I conditions, and it became obvious that the different morphologies affected the resulting interlaminar fracture energies (G I C ) in different ways. In general, it can be stated that a coarse spherulitic morphology results in lower values of fracture energy, mainly due to interspherulitic fracture phenomena. The additional effects of crystallinity for the same spherulitic size were also analyzed.