The present work provides a detailed analysis of the segregation induced hydrogen embrittlement in metals. Based on the assumption that the ductile versus brittle transition is controlled by the competition between dislocation emission and interfacial decohesion, hydrogen-induced embrittlement (HIE) is believed to occur due to the reduction of cohesion induced by segregation of hydrogen. A thermodynamic-kinetic model for the change in cohesion induced by segregation is proposed. In particular, the mobility related characteristics of HIE is addressed. It is shown that a “mobile” normal segregant reduces the cohesion greater than an “immobile” segregant does. For HIE in steels, a transient behavior occurs at room temperature because of the high diffusivity of hydrogen in iron. The model predictions are supported by experimental results for Fe–3%Si alloys and nickel.