Physical activity is widely recognised for its health benefits, yet many individuals fail to meet recommended exercise guidelines. Enjoyment is an important factor in sustaining physical activity; however, stress can significantly lower this enjoyment. This study investigates how stress affects expected enjoyment in physical activity, with a focus on the mediating role of perceived barriers and expected effort. Additionally, the study explored the role of approach versus avoidance tendencies as a potential moderator. A sample of 127 students completed a survey that included a stress-inducing pilot text. Results indicated that stress significantly reduced expected enjoyment in physical activity, with significant mediation through expected effort and no significant mediation through perceived barriers. The stress-inducing text effectively decreased expected enjoyment, showing promise as an easy, cost-effective method to manipulate stress in future research. Findings suggest interventions to enhance exercise adherence by reducing effort perceptions of PA.