Missing data are a persistent problem in psychological research. Peer nomination data present a unique missing data problem, because a nominator's nonparticipation results in missing data for other individuals in the study. This study examined the range of effects of systematic nonparticipation on the correlations between peer nomination data when nominators with various levels of popularity and social preference are missing. Results showed that, compared to completely random nominator missingness, systematic missingness of raters based on popularity had a significant impact on the correlations between various peer nomination variables. Systematic missingness based on social preference had a smaller impact. These results demonstrate varying (and potentially large) effects of systematically missing nominators on studies using nomination data. It is important that researchers using peer nomination data explore whether nominators are missing in any sort of systematic way and include these results as part of each study. Future research into the nature of systematic nominator missingness could make it possible to use advanced methodologies, such as multiple imputation, in an attempt to minimize the issues associated with systematic missingness.