This study examines longitudinal associations among reading skills, math skills and emotional well-being in a Finnish sample (n = 586) followed from the end of comprehensive school (Grade 9, age 15-16) to age 20. In particular, we determine whether the associations between skills and well-being are mediated by self-concept beliefs. In Grade 9, the participants' reading fluency, PISA reading comprehension and math skills were assessed in classrooms, and questionnaires were used to assess self-concept (global and skill-specific) and internalising problems. At age 20, questionnaires were used to self-report emotional well-being and educational attainment. The results showed no direct predictive association between academic skills and age-20 emotional well-being, while indirect effects from academic skills on emotional well-being were found for reading skills through reading comprehension self-concept belief and educational attainment and for math skills through global self-concept belief. In addition, adolescent global self-concept and internalising problems predicted age-20 emotional well-being. The results suggest that adolescent self-concept beliefs and internalising problems, rather than academic skills per se, can predict emotional problems in young adulthood.