There is little knowledge available concerning psychopathic traits in Asian adolescents; a lack of a suitable measurement instrument for assessing psychopathy in Asian societies may account for this. This study aimed to validate a widely used scale in the West — the Antisocial Process Screening Device (APSD) — in Singaporean school-based and at-risk adolescents. Using an exploratory factor analysis (EFA) and a confirmatory factor analysis (CFA), this study examined the two-factor (i.e., grandiose-manipulative/impulsive traits and callous-unemotional traits) and three-factor (i.e., grandiose-manipulative traits, impulsivity, and callous-unemotional traits) models of the APSD in 1027 school-based and 113 at-risk adolescents. School samples are adolescents from three secondary schools, while at-risk samples are adolescents who manifest different types of delinquent behaviors and are either placed in more structured settings or need closer supervision although they have not violated the law. Gender invariance was further tested in the school-based sample by conducting a multigroup CFA. The convergent validity of the APSD was also investigated in the school-based sample. For the school-based adolescents, the APSD revealed that the three-factor model provided a superior fit over the two-factor model and the factorial invariance across gender. Significant relationships between the three dimensions of the APSD and aggression and delinquency support the convergent validity of the APSD. As for the at-risk adolescents, both the two- and three-factor models were acceptable, but the two-factor model was preferred as it was parsimonious and it aligned with the conceptualized characteristics of psychopathic traits. Findings suggest that the APSD is a reliable and sound instrument for measuring psychopathic traits in Asian school-based and at-risk adolescents.