This study examined the role of stress on irrational health beliefs and health behaviors among individuals 18-45 years old. Previous research has shown that this age group reported higher stress levels, more physical symptoms of stress, and the highest level of negative health behaviors. The theoretical frameworks were health belief model, the transactional model of stress and coping theory, and Ellis's concept of irrational beliefs. A survey using 3 published instruments measured the perceived stress level, irrational health beliefs, and health behaviors of a sample of 97 individuals aged 18-45. The data were quantitatively assessed using a mediation model to test a significant relationship between the predictor variable, perceived stress, and the criterion variable, health behaviors, using the mediating variable of irrational health beliefs. Findings suggest that higher stress levels are related to health behaviors (p ˂ .001), while stress did not make a significant contribution to irrational health beliefs (p = .092). Moreover, findings indicated that greater irrational health beliefs are related to more negative health behaviors (p = .010). Irrational health beliefs were not found to mediate the relationship between perceived stress and health behaviors. This research supports and extends the current body of research examining the relationship between stress, irrational health beliefs, and health behaviors. The results of this study can provide insight into how stress is related to thoughts and behaviors, specifically focusing on health. This study may aid health psychologists by providing information that can contribute to the development of interventions to reduce stress, reduce irrational health beliefs, and improve health behaviors.