This study aims to better our collective understanding of the oxidative capacity and atmospheric chemistry over the equatorial Pacific. Bulk and size-segregated filter samples were collected during the GEOTRACES Eastern Tropical Pacific transect (4.1° S, 81.9° W to 10.5° S, 152.0° W; October–December 2013) and measured for aerosol concentration and complete isotopic composition of nitrate (δ15N, δ18O, Δ17O where Δ17O = δ17O – 0.52 × δ18O). Combined size-segregated filters produced data similar to that found in bulk filter samples, and notably neither δ15N nor δ18O showed any trends based on aerosol size. Similar to other studies, NO3– is concentrated (>80%) in the coarse size fractions (>1.5 μm). Bulk aerosol concentrations ranged from 6.6 to 89.8 nmol/m3. The bulk δ15N-, δ18O-, and Δ17O-nitrate ranged from −13.1 to −3.2‰, 68.5 to 79.3‰, and 23.5 to 28.4‰, respectively. Higher δ15N values near the coast are best explained by the influence of continental sources; lower δ15N values far from the coast may be associated with chemical fractionation during long-range transport or an oceanic source. Both Δ17O and δ18O are interpreted using kinetic analysis and gas concentrations from a global atmospheric chemical transport model (GEOS-Chem), which showed that nitrate production in this environment is dominated by OH oxidation (60%) and RONO2 hydrolysis (15%). To best match the δ18O and Δ17O observations in this study, the terminal oxygen isotopic values for ozone must be higher than those suggested by available observations and/or halogen-mediated chemistry must be more important than the models currently suggest.