Although personal and environmental correlates of adolescents' happiness have been found, the temporal direction of these relationships is less known. The present study explored the longitudinal and reciprocal relationships between self-esteem, school adjustment, and happiness during secondary school years in South Korea. Longitudinal data of 2,351 adolescents from three time points (Grades 7, 9, and 11) were drawn from the Korean Children and Youth Panel Survey (KCYPS) and were analyzed using autoregressive cross-lagged modeling. The results indicated that inter-individual differences in self-esteem, school adjustment, and happiness were moderately stable from Grades 7 to 11. Self-esteem and happiness, and self-esteem and school adjustment reciprocally predicted each other over time. The effects of self-esteem on happiness and school adjustment two years later were stronger than the reverse direction of effects. School adjustment and happiness were only indirectly interrelated through self-esteem over time. These longitudinal relationships did not differ between genders. The implications of the findings for future research and adolescent interventions are discussed.