The spirituality and religiosity of Indonesian Muslim adolescents were examined longitudinally as were the relations of spirituality and religiosity with (mal)adjustment. At Time 1 (T1), 959 seventh-grade Muslim adolescents were screened for selection of a sample; at Time 2 (T2), 183 eighth-grade adolescents participated; and at Time 3 (T3), 300 ninth-grade adolescents (164 new participants) participated. At T1, adolescents' peer likeability was assessed; at T2, adolescents' global and cognitive esteem were measured; and at T2 and T3, adolescents' (mal)adjustment, spirituality, and religiosity were assessed. Adolescents and parents rated aspects of (mal)adjustment, spirituality, and religiosity. Teachers also rated adolescents' (mal)adjustment. In general, we found that T2 spirituality and religiosity were positively related to T3 adjustment and negatively related to T3 maladjustment, although in panel models, support for prediction of outcomes from spirituality and religiosity was found only for loneliness and socially appropriate behavior. In addition, there was some evidence in the models that certain aspects of (mal)adjustment (self-esteem and social competence, and to a marginal degree, parent-rated internalizing problems and teacher-rated prosociality) predicted spirituality and religiosity longitudinally. (Contains 7 tables and 4 figures.)