Injection molding of semicrystalline plastics was simulated with the proposed Stress-induced crystallization model. A pseudo-concentration method was used to track the melt front advancement. Stress relaxation was considered using the WFL model. Simulations were carried out under different processing conditions to investigate the effect of processing parameters on the crystallinity of the final part. The simulation results reproduced most of the experimental results in the literature. Comparison is made between the slow-crystallizing polymer (PET) and fast-crystallizing polymer (PP) to demonstrate the effect of stress on the crystallization kinetics during the injection molding process for materials with different crystallization properties. The results show that for fast-crystallizing plastics, stress has little effect on the final crystallinity in the injection molded parts.