Although proton exchange membrane (PEM) water electrolyzers offer a promising means for generation of hydrogen fuel from solar and wind energy, in acidic environments the corresponding anodic oxygen evolution reaction (OER) remains a bottleneck. Because the activity and stability of electrocatalysts depend significantly on physicochemical properties, material surface and interface engineering can offer a practical way to boost performance. To date, significant advances have been made using a judicious combination of advanced theoretical computations and spectroscopic characterizations. To provide a critical assessment of this field, we focus on the establishment of material property–catalytic activity relationships. We start with a detailed exploration of prevailing OER mechanisms in acid solution through evaluating the role of catalyst lattice oxygen. We then critically review advances in surface and interface engineering in acidic OER electrocatalysts from both experimental and theoretical perspectives. Finally, a few promising research orientations are proposed to inspire future investigation of high-performance PEM catalysts.