The purpose of the present study is to validate the Happiness Meta-cognition Questionnaire which measures adolescents’ ability in happiness meta-cognition. Participants were 252 high school students (100 males, 152 females). All participants completed the Happiness Meta-cognition Questionnaire, the Positive Mental Health Scale, Self-efficacy Scale, IPPA-R and the Korean Version of Perceived Stress Scale. The result of inter-rater reliability between the raters showed an adequate level, thus indicating that the Happiness Meta-cognition Questionnaire is a reliable assessment tool. To confirm the criterion-related validity, we administered the correlation analysis between happiness meta-cognition and the mental health variables. The results showed that happiness meta-cognition positively correlated with self-efficacy and peer relationships, while negatively correlated with perceived stress. According to positive mental health types, flourishing type showed higher happiness meta-cognition than languishing and floundering type, and struggling type higher than floundering type. Lastly, the implications of the present study and suggestions for future research were discussed.