The current study assessed associations among theoretically driven measures of ethnic identity and psychosocial adjustment among 137 Navajo adolescents. For both sexes, measures of students' sense of affirmation and belonging to their ethnic heritage emerged as a strong predictor of positive psychosocial functioning. Less-consistent patterns of association emerged between other measures of ethnic identity and psychosocial adjustment. Students with achieved ethnic identity status, characterized by high levels of exploration of their ethnic heritage and high levels of affirmation or commitment to their Navajo culture, reported the most positive functioning on several measures. Interesting interactions with biological sex suggested that ethnic identity may function differently for male and female Navajo adolescents. Implications of results for educators, parents, and policy makers are discussed. (Contains 2 tables.)