The positive online behavior effects of digital citizenship have increasingly attracted the attention of scholars. This study designed and tested the psychometric properties of an Adolescent Digital Citizenship Scale (DCS-A) in two independent samples of Mexican secondary students (Sample 1, M age = 13.2 years, SD = 1.5 and Sample 2, M age = 13.4 years, SD = 1.4; N1 = 750, N2 = 750). We examined content, factorial, discriminant, concurrent validity, and reliability. We also tested the cross-sample and gender invariance. Confirmatory factor analysis (CFA) demonstrated goodness-of-fit on a second-order factorial model that displays three first-order factors (online ethic, online civic engagement, and online diversity acceptance). Cross-validation confirmed the factorial structure stability of the DCS-A across the independent sample. The result demonstrated the equivalence of the measurement model in both genders (configural, metric, and scalar invariance). The latent means comparison indicates that females held greater online ethics, online civic engagement, and online inclusive behaviors than males. Finally, the concurrent validity of the scale was supported by finding a positive relationship between DCS-A dimensions and defender behavior and a negative association with passive and reinforces interventions in cyberbullying events. These results suggest that the DCS-A is a theoretically and psychometrically grounded measure of digital citizenship in adolescents.