Purpose of Review <p>Geogenic As enrichment occurs in alpine riverine systems worldwide, while the understanding of the facilitation of DOM transformation on As enrichment remains unclear. This review aims to summarize the typical occurrence of As anomaly and the principal components of DOM in global alpine river systems, and evaluate the critical pathways of DOM participating in As mobilization under different geochemical scenarios.</p> Recent Findings <p>DOM constitutions in alpine riverine systems were distinct from downstream urbanized river basins due to the glacier degradation, atmosphere pollution, and permafrost thawing, etc. Notably, the diverse functional groups in DOM could potentially affect As mobility through triggering the As-bearing mineral transformation, changing As redox species, competitive adsorption, and the formation of surface complex species. The formation of the ternary DOM-Fe-As complex is also critical for controlling the As mobility in the water–sediment interface.</p> Summary <p>Future study should focus on the long-term and high-resolution monitoring of spatial-temporal variations in the concurrent transformations in DOM and As in alpine riverine systems, and it is urgent to utilize comprehensive characterization technologies in combination with <i>state-of-the-art</i> statistical analysis for quantitatively refining our understanding on the detailed mechanism accounting for the facilitation of DOM transformation on As enrichment in alpine riverine system, which is fundamental for developing remediation technologies for geogenic As enrichment and securing the safe drinking water supply in headwater regions globally.</p>