Self-concept is a significant factor in the interpersonal and academic success of students, especially those who attend an alternative school because of learning disabilities or behavioral challenges. Previous studies have shown sex and age differences in global or unidimensional self-concept; however, none has explored sex and age differences in multidimensional self-concept among special needs students in alternative schools. Grounded in the foundation of the Shavelson-Marsh theory of hierarchical academic self-concept, this quantitative study explored the extent to which sex-and age-differentiation influenced self-concept among students attending an alternative school. Using the Piers-Harris Children's Self Concept Scale 2 (PHCSCS-2), self-concept was assessed in 6 domains (behavioral adjustment, intellectual and school status, physical appearance and attributes, freedom from anxiety, popularity, and happiness and satisfaction) of 37 male and 37 female students attending a suburban alternative school. Multivariate analysis of variance determined that sex differences existed in only one domain: Female students had higher levels of self-concept in the intellectual and school status domain. Analysis further indicated that age was not a mediating factor in self-concept. The implications for positive social change include building support for interventions intended to enhance self-concept of special needs students. Interventions to improve self-concept can help students to develop and enhance the skills necessary for a successful future. When counselors, educators, and administrators develop and implement age-and sex-appropriate strategies to improve student's self-concept, students will be better prepared to function academically, socially, and interpersonally.