Concentrations and the stable isotopic composition of bulk aerosol nitrate (NO₃^-) were quantified from two fall GEOTRACES cruises: 1) Alaska–Tahiti (GP15; n=22) and 2) Peru–Tahiti (GP16; n=17) to explore the hypothesis that marine emissions influence aerosol NO₃^- in the Equatorial Pacific. The δ¹⁵N-NO₃^- ranged from -14.5–0.5‰, with lowest values far from the coast and primarily reflecting a shift in sources. The δ¹⁸O- and Δ¹⁷O-NO₃^- were both high (65.2–85.4‰ and 21.4–30.7‰, respectively) and decreased away from continental regions, reflecting a shift in the oxidants that influence the formation of NO₃^-. Transport modeling and co-occurrence of low δ¹⁵N, δ¹⁸O and Δ¹⁷O provided evidence for an important influence of alkyl nitrates (RONO₂) on aerosol NO₃^- formation. Based on the Δ¹⁷O, we quantified that the contribution of RONO₂ to aerosol NO₃^- can be as high as 48% (range 15–48%). We were also able to estimate an average δ¹⁵N-RONO₂ of -22.9 ± 19.1‰.