The climate crisis demands a rapid reduction in greenhouse gas emissions, placing renewable energy technologies and green hydrogen at the center of future carbon-neutral energy strategies. Proton Exchange Membrane Water Electrolysis (PEMWE) is a key technology for high-purity hydrogen production, providing high efficiency and rapid response to fluctuating power inputs. This work develops a unified multiphysics modeling framework for PEMWE with focus on the Nafion membrane (PEM) and anode Catalyst Layer (aCL). Nafion is a perfluorosulfonic acid polymer characterized by a nanostructured porous morphology composed of hydrated ionic channels embedded within a polymer matrix. Water uptake enables proton conduction, while fixed anionic groups govern the electrochemical and mechanical response of the membrane. The framework is formulated within the Theory of Porous Media (TPM) and the Theory of Mixtures (TM), enabling a consistent description of the coupling between membrane deformation, water transport, and proton migration under chemical and electrical gradients. Beyond electrochemical transport, this study extends prior research on fracture modeling in PEMWE by incorporating fluid flow in porous media and examining how fracture initiation alters transport pathways and pore pressure distributions in aCL. Darcy-based flow modeling is integrated with a phase-field formulation for fracture, with permeability and porosity expressed as functions of the phase-field variable. A poroelastic description accounts for fluid–solid interactions and stress redistribution during crack growth, allowing the model to capture anisotropic transport and progressive performance degradation associated with Catalyst Coated Membrane (CCM) failure. In addition, the framework incorporates chemomechanical fracture mechanisms driven by proton accumulation during the Oxygen Evolution Reaction (OER). Local increases in proton concentration within confined hydrated domains promote stress localization and crack initiation in the domain. By consistently integrating these effects, the proposed approach provides a more comprehensive understanding of electro-chemo-hydro-mechanical degradation in PEMWE systems and their influence on long-term performance.