This study simulates the tensile failure of injection-molded short glass fiber-reinforced polyamide 6,6 (GF/PA66). Tensile tests of unreinforced PA66 are first conducted and the material properties are obtained by fitting a simulated stress strain curve to the experiment result. Using the obtained material properties, failure simulations of GF/PA66 composites are performed for four types of specimens with various fiber lengths and fiber orientation distributions. In the simulations, multiscale mechanistic model, which can simulate micromechanical damage, and Micromechanics Model (MM), which has very low computational cost, are adapted and the results are compared with experiments. Both models reproduce the experiment results well. Considering the computational cost, MM is the better model for predicting the failure properties of GF/PA66 composites. (C) 2013 Elsevier Ltd. All rights reserved.