Experimental studies indicate a deleterious influence of a hydrogenous environment on the fatigue crack propagation resistance of metallic materials. In order to provide a predictive tool to assess fatigue lifetime of structures subjected to hydrogen, an ABAQUS finite element model of a compact tension (CT) specimen has been developed. A cohesive zone model (CZM) with a specific traction-separation law is used in conjunction with an elastic-plastic bulk material to model fatigue crack growth. The traction-separation law has been developed to take into account the influence of cyclic loading on crack propagation. A special attention has been paid to develop the model in the framework of thermodynamics, i.e. to ensure that the dissipation remains positive at any time. In addition, the parameters of the traction-separation law depend on local hydrogen concentration. This traction-separation law was implemented using ABAQUS user element subroutine UEL which is used to predict the influence of hydrogen on fatigue crack growth rates. Given the similarity between heat and mass diffusion equations, the coupling between hydrogen diffusion and the mechanical behaviour of the material has been implemented using ABAQUS coupled temperaturedisplacement procedure.