ABSTRACT Introduction Using the metacognitive model of emotion dysregulation as a basis, this study explored whether metacognitive beliefs are associated with positive emotion dysregulation. Method A total of 436 participants from the general population and 133 outpatients seeking psychological treatment were recruited. Positive emotion dysregulation, metacognitive beliefs, and affective symptoms were assessed. T t test, chi‐square test, correlation, and hierarchical multiple linear regression analyses were run. Results In the general population, over and above age, sex, and affective symptoms, a higher endorsement on positive beliefs about worry, negative beliefs about thoughts concerning uncontrollability and danger, and beliefs about the need to control thoughts were associated with a poor acceptance of positive emotions ( F = 13.66, p < 0.001), with difficulties in engaging in goal‐directed behavior ( F = 9.06, p < 0.001), and with difficulties in controlling behaviors when experiencing positive emotions ( F = 10.61, p < 0.001). In the clinical sample, over and above age, sex, and affective symptoms, a higher endorsement of negative beliefs about thoughts concerning uncontrollability and danger and lack of cognitive confidence were associated with difficulties in engaging in goal‐directed behavior ( F = 5.74, p < 0.001) and with difficulties in controlling behaviors when experiencing positive emotions ( F = 6.54, p < 0.001). Outpatients seeking psychological treatment also reported more severe positive emotion dysregulation and higher endorsement of metacognitive beliefs when compared with the general population ( p < 0.001). Conclusion Positive emotion dysregulation appears to be associated with the tendency to endorse metacognitive beliefs. Metacognitive beliefs could be a potential therapeutic target for reducing difficulties in the regulation of positive emotions. Summary Among participants from the general population, the tendency to endorse metacognitive beliefs is associated with greater positive emotion dysregulation. Among outpatients seeking psychological treatment, the tendency to endorse metacognitive beliefs is associated with greater positive emotion dysregulation. Assessing metacognitive beliefs may allow clinicians to gain a clearer understanding of treatment trajectories to reduce difficulties in the regulation of positive emotions. Metacognitive beliefs could be the potential therapeutic target to reduce positive emotion dysregulation. Metacognitive Therapy techniques could be suitable approaches to reduce positive emotion dysregulation.