(1) Background: Adherence to treatment and medical check-ups are important for health outcomes, but low adherence to treatment is a common phenomenon. Thus, we aimed to examine the role of cultural beliefs about physicians, perceived mistreatment, and emotions associated with the experience of mistreatment as an antecedent of healthcare behavior among Chilean and Mexican primary care patients using Betancourt’s model for the study of health behavior. (2) Methods: This is a multivariate cross-sectional study with a non-probabilistic sample of 326 Mexican and 337 Chilean participants. Multigroup structural equation modeling was used to test the structural relations among the cultural and psychological variables as determinants of healthcare avoidance behavior. (3) Results: The results revealed a pattern of associations that work in the same way for Chilean and Mexican samples. Negative cultural beliefs about physicians have a direct effect on avoidance behaviors in healthcare. In addition, this effect is mediated through psychological factors, such as perception of mistreatment and negative emotions associated with mistreatment. (4) Conclusions: A structural invariance test showed that the perception of mistreatment and negative emotions were less intense for Chileans than Mexicans. In contrast, the association between negative emotions and avoidance behaviors was less intense for Mexicans.