Positive Youth Development (PYD) model is a strength-based perspective of transition to adulthood derived from developmental systems theory. Developmental assets (DAs) framework describes the individual and contextual resources that may promote PYD. This work aims to analyze the associations between internal and external DAs and PYD, as well as examining gender differences, in Spanish youth. Data of students enrolled in 10 high schools and universities, collected in the PYD Cross-National Project in Spain through a self-report instrument, were used. Structural equation modeling showed that DAs were positively related to PYD. Some gender differences were observed in PYD, such that male students presented higher scores in confidence and competence, and female students showed more connection, caring, and character. Results of partial mediation modeling indicated that these gender differences in PYD may be partly explained by gender differences in DAs.