The study of personality in nonhuman primates has increased substantially, but most studies so far have been conducted with captive animals. In addition, few studies investigated the personality of Neotropical (Platyrrhini) monkeys. If we aim at investigating the ecological and social significance of personality in nonhuman primates, conducting studies of wild populations and covering a wide range of taxa is essential. In this study, we analyzed the personality structure of a wild group of Neotropical monkeys, the yellow-breasted capuchin (Sapajus xanthosternos). We adopted two widespread methods: trait rating, using the Hominoid Personality Questionnaire, and behavioral coding, analyzing 13 behaviors and 3 derived variables. We described 3 traits with trait rating, labeled Openness-Neuroticism, Assertiveness, and Attentiveness-Sociability. We also described 3 traits with behavioral coding, labeled Prosociality, Aggressiveness, and Reactivity to Humans. Comparing both methods we found not only broad convergences between the structures obtained (e.g., both showed prosocial and aggressive traits) but also some differences (e.g., Openness-Neuroticism was not clearly defined with behavioral coding), concluding that combining both methods provided complementary findings. Some socioecological variables seem to influence the expression of personality in captive versus wild living monkeys. For example, in our study, assertive individuals were more vigilant, whereas in the studies in captivity, neurotic individuals were more vigilant. These questions highlight the need for more research in wild conditions and enlarging the number of species and populations studied. (PsycInfo Database Record (c) 2020 APA, all rights reserved).