AbstractIsolated or contiguous, the surface distributions of Pd atoms in the Pd−Au bimetallic nanoparticle (NP) catalysts often influence activity and selectivity towards specific reactions. In this study, we used a concomitant Pd hydride formation upon H2 exposure as a probe of presence of contiguous Pd regions in bimetallic NPs. For demonstrating this method, we prepared silica supported monometallic Pd and bimetallic Pd−Au NPs with a Pd/Au ratio of 25/75 (Pd25Au75) and used X‐ray absorption spectroscopy, scanning transmission electron microscopy and infrared spectroscopy to detect and quantitatively analyze the Pd hydride regions. This work provides a new approach to characterizing intra‐particle heterogeneities within the bimetallic NPs at ambient temperature and pressure.