This goal of this study was to develop a measure that captures the three dimensions of youth purpose proposed by Damon, Menon, and Cotton-Bronk (2003). We tested a theoretical model that links youth purpose (comprised of intention, engagement, and prosocial reasoning) with achievement motivation, agency, and civic engagement for a sample of high school and college-aged adolescents. Results for the new measure of youth purpose reveal a three factor model that indirectly predicts civic engagement, as partially mediated by achievement motivation and agency. Limitations and suggestions for future research are discussed.