The basic aim of this research is to examine the mediating role of perceived stress between metacognition and happiness. The participants were 290 university students. In this study, the Metacognition Questionnaire-MCQ-30, the Perceived Stress Scale and the Short Form of Oxford Happiness Questionnaire were used. The relationships between metacognition, perceived stress, and happiness were examined using correlation analysis and Structural Equation Model (SEM). In correlation analysis, metacognition and perceived stress were found to be negatively related to happiness. On the other hand, metacognition was found to be positively correlated to perceived stress. Structural Equation Model showed that metacognition results in an increase in perceived stress in an unhappy person, whereas reduction in stress leads to happiness; however, metacognition also produces unhappiness. Results were discussed in the light of the related literature.