We quantify the stellar abundances of neutron-rich r-process nuclei in cosmological zoom-in simulations of a Milky Way-mass galaxy from the Feedback In Realistic Environments project . The galaxy is enriched with r-process elements by binary neutron star ( NS ) mergers and with iron and other metals by supernovae . These calculations include key hydrodynamic mixing processes not present in standard semi-analytic chemical evolution models , such as galactic winds and hydrodynamic flows associated with structure formation . We explore a range of models for the rate and delay time of NS mergers , intended to roughly bracket the wide range of models consistent with current observational constraints . We show that NS mergers can produce [ r-process/Fe ] abundance ratios and scatter that appear reasonably consistent with observational constraints . At low metallicity , \mathrm { [ Fe / H ] } \lesssim - 2 , we predict there is a wide range of stellar r-process abundance ratios , with both supersolar and subsolar abundances . Low-metallicity stars or stars that are outliers in their r-process abundance ratios are , on average , formed at high redshift and located at large galactocentric radius . Because NS mergers are rare , our results are not fully converged with respect to resolution , particularly at low metallicity . However , the uncertain rate and delay time distribution of NS mergers introduces an uncertainty in the r-process abundances comparable to that due to finite numerical resolution . Overall , our results are consistent with NS mergers being the source of most of the r-process nuclei in the Universe .