Resumen: Background: During the various stages of education, adolescents undergo emotional and motivational experiences that can play key roles in their development. This study aims to analyse the relationship among academic self-efficacy, optimism, and academic performance. Methods: This study comprised 1852 adolescent (male, N = 956, 51.61% and female, N = 896, 48.38%) aged 12–19 years (M = 14.77; SD = 1.80) from twelve secondary schools in Spain. The instruments used for the evaluation were the Academic Self-Efficacy Scale (ASES) and the Life Orientation Test—Revised (LOT-R); the students’ average marks were used to measure their academic performance. Results: The results of the study revealed significant correlations among self-efficacy, optimism and academic performance. Conclusions: These results emphasise the importance of academic self-efficacy as a mediating variable between the other two variables as well as its central role in the promotion of adaptive behaviours in the classroom, leading to adequate personal development, helping to prevent early school dropout and contributing to a more satisfactory academic experience. Idioma: Inglés DOI: 10.3390/children9030420 Año: 2022 Publicado en: Children 9, 3 (2022), 420 [10 pp.] ISSN: 2227-9067 Factor impacto JCR: 2.4 (2022) Categ. JCR: PEDIATRICS rank: 58 / 130 = 0.446 (2022) - Q2 - T2 Factor impacto CITESCORE: 2.0 - Medicine (Q3)