Resolving the origin and flowpaths of meltwaters in Arctic glacierized catchments, beyond the traditional atmospheric versus water-rock framework, is crucial for understanding how weathering processes evolve with glacier retreat and regulate solute export. We investigated the hydrochemistry and isotopic composition of glacial meltwaters and proglacial streams in the Kongsfjorden region (Svalbard), integrating major ions and stable water isotopes with coupled 87Sr/86Sr and δ11B analyses during the early melt season. Major ion systematics reveal a dominant marine aerosol imprint, indicating that early meltwater chemistry is largely controlled by snowpack flushing of sea-spray deposits accumulated in the winter snowpack. Strong Na–Cl correlations and B/Na ratios close to those of seawater support this interpretation. Nevertheless, sea-salt corrections and isotopic tracers demonstrate measurable crustal contributions. Radiogenic 87Sr/86Sr values (>0.720 in the Midtre Lovénbreen and Kongsvegen basins) cannot be explained by marine input or carbonate dissolution alone and instead require interaction with rubidium (Rb)-rich siliciclastic or metamorphic lithologies. Boron isotopes further constrain the relative contribution of these sources, with estimated marine B fractions ranging from approximately 30%–80% across catchments. Coupled 87Sr/86Sr–δ11B isotope systematics identify mixing between a marine aerosol component and at least two crustal end-members (carbonate and metamorphic/siliciclastic), highlighting glacier-specific differences linked to hydrological routing and local geology. Our results show that the combined use of Sr and B isotopes provides a powerful geochemical framework to disentangle atmospheric marine inputs from crustal weathering processes in Arctic glacial meltwaters. They further indicate that, even under early melt-season conditions dominated by snowpack flushing, water–rock interaction still modulates meltwater chemistry. This study represents the first application of δ11B isotopes to Arctic glacial and proglacial waters and one of the few investigations employing Sr isotopes in Arctic continental meltwater systems. The integrated 87Sr/86Sr–δ11B framework provides a robust isotopic baseline for assessing evolving weathering regimes and solute export pathways in rapidly changing polar environments.