Despite previous research on adolescence points to an association between social competence and well-being, limited knowledge is available. Most studies have documented a one-way pattern of influence, although reciprocity has also been suggested. However, they mainly use a cross-sectional design, do not focus on psychological well-being, and do not use integrative and multidimensional constructs. From a eudaimonic approach to well-being and situation-specific to social competence, this study aimed to: (1) explore the factorial structure of the dimensions assessed; (2) analyse the longitudinal relationship between psychological well being and social competence during adolescence; and (3) examine psychological well-being and social competence levels and their stability over time. The sample consisted of 662 adolescents aged between 14 and 16 years old (Time 1 Mage = 14.63; SD = 0.64; 51% girls). Structural equation analysis confirmed the existence of second-order factors, showing evidence of a positive and bidirectional relationship between psychological well-being and social competence. Results also revealed medium–high levels in both constructs, which remained stable over time. These findings highlight the importance of promoting both psychological well-being and social competence to achieve successful, healthy development.