The two broad aims of this study were to (a) investigate how the three traits of the triarchic model—boldness, meanness, and disinhibition—relate to compliance with public health measures, as well as to internalizing and externalizing psychopathology, during a public health crisis, and (b) test for associations between psychopathology and compliance with public health measures. Participants were 947 Brazilian adult females aged 18–75 years who completed measures of the triarchic traits, internalizing and externalizing symptoms/problems, and a COVID-19 behaviors and beliefs questionnaire. Multiple regression and path analyses showed meanness to be the only triarchic trait significantly predictive of compliance with public health measures, in a negative direction, when controlling for the other traits. Results also demonstrated that compliance with public health measures was associated with levels of distress (negatively), obsessions/fear (positively), and positive mood (negatively). Overall, the results demonstrate the contributions of the triarchic traits to understanding complex phenomena, highlighting meanness as the most essential triarchic trait predictor of adherence to public health measures among females.