Plasmonic photocatalysis, which represents a paradigm-shifting approach to solar-to-chemical energy conversion, has become a rapidly evolving research field full of opportunities, challenges, and open questions. Plasmon-driven photocatalytic reactions are mechanistically complex, dictated not only by multiple interplaying photophysical effects but also by local chemical environments at the catalyst–adsorbate interfaces. This review article highlights the unique value of plasmon-enhanced Raman spectroscopy in mechanistic studies of plasmonic photocatalysis. Using plasmon-driven reductive coupling of nitroarene derivative adsorbates as a model reaction system, this article elaborates on how the rich information extracted from deliberately designed plasmon-enhanced Raman spectroscopic measurements can be carefully analyzed and further rationalized to generate critical insights into the exact roles of hot carriers, photothermal transduction, and catalyst–adsorbate interactions in plasmonic photocatalysis.