A numerical framework is developed in this paper to study hydrogen embrittlement. A hydrogen diffusion equation is derived, and a trapping density function is proposed in the framework of the phase field model. Effect of hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion (HEDE) are modeled by reducing the yield stress and decreasing the critical energy release rate respectively. Simulation results of a compact tension specimen and a double notched tension specimen show that hydrogen accumulates at the crack/notch tip region driven by positive hydrostatic stress as well as more traps produced by plastic deformation in this area. Both HELP and HEDE reduce the load carrying capacity of the specimen, and their effects depend on the model parameters. The proposed model provides a numerical tool that can be used to comprehensively simulate hydrogen embrittlement and predict the ductile to brittle transition of the material due to the presence of hydrogen. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.