Climate change is expected to alter the input of nitrogen (N) sources in the Eastern Canadian Arctic Archipelago (ECAA) and Baffin Bay due to increased discharge from glacial meltwater and permafrost thaw. Since dissolved inorganic N is generally depleted in surface waters, dissolved organic N (DON) could represent a significant N source fueling phytoplankton activity in Arctic ecosystems. Yet, few DON data for this region exist. We measured concentrations and stable isotope ratios (δ15N and δ18O) of DON and nitrate (NO3−) to investigate the sources and cycling of dissolved nitrogen in regional rivers and at the sea surface from samples collected in the ECAA and Baffin Bay during the summer of 2019. The isotopic signatures of NO3- in rivers could be reproduced in a steady state isotopic model by invoking mixing between atmospheric NO3- and nitrified ammonium as well as NO3- assimilation by phytoplankton. DON concentrations were low in most rivers (≤4.9 µmol L−1), whereas the concentrations (0.54–12 µmol L−1) and δ15N of DON (−0.71–9.6 ‰) at the sea surface were variable among stations, suggesting dynamic cycling and/or distinctive sources. In two regions with high chl-a, DON concentrations were inversely correlated with chlorophyll‐an and the d15N of DON, suggesting net DON consumption in localized phytoplankton blooms. We derived an isotope effect of −6.9‰ for DON consumption. Our data helps establish a baseline to assess future change in nutrient regime for this climate sensitive region.