Objective Previous research has shown that self-esteem is associated with academic achievement. However, few studies have used longitudinal data to examine how self-esteem and achievement co-develop over a long time span, and even fewer have focused on ethnic minority youth. Method We used data from a longitudinal study of Mexican-origin youth (N = 674) to examine the bidirectional associations between self-esteem and academic achievement from 5th to 11th grade. Global and domain-specific self-esteem (academic, honesty, peer relationships, appearance) were assessed at ages 10, 12, 14, and 16 using Marsh et al.'s (2005) Self-Description Questionnaire. Academic achievement was assessed at the same ages using self-reported grades and standardized test scores from school records. Results Youth with high global and academic self-esteem showed relative improvements in their grades (but not test scores), and youth who received higher grades and test scores showed relative increases in global and academic self-esteem. Youth with high honesty self-esteem showed relative increases in grades and test scores, and youth with higher grades showed relative increases in peer relationship self-esteem. Conclusion Students who feel better about themselves tend to show improvements in their grades, and getting better grades and test scores promotes more positive self-views.