Background: The objective was to predict early adolescents' emotional well-being from personal and contextual assets in the classroom. Emotional well-being is a key indicator of health. Aligned with the positive youth development (PYD) framework, a supportive classroom environment and positive relationships with teachers and peers were contextual assets in the present study; positive self-concept was a personal asset. Methods: The sample was 406 grade 4 to 7 public elementary school students from diverse backgrounds (mean = 11.27 years; SD = 0.89; 50% female). Data were self-, teacher-, and peer-reported. Structural equation modeling (SEM) analyses were used to evaluate model fit and identify significant pathways. Results: SEM indicated a good model fit. Overall, 68% of variability in early adolescents' emotional well-being was explained. Positive self-concept directly predicted emotional well-being. Supportive classroom environment predicted emotional well-being directly and indirectly through increases in positive social relationships and self-concept. Positive social relationships predicted well-being only indirectly through positive self-concept. Conclusions: Contextual and personal assets are central for early adolescents' emotional well-being. The interrelation among assets needs to be considered when understanding, and ultimately promoting students' emotional well-being. The present findings extend previous research and inform school-based intervention and prevention programming and teacher professional development.