Recent studies have consistently demonstrated that antisocial behaviors occur in online environments. Although online antisocial behavior has a long history, it appears to have become more widespread in recent years due to the widespread use of online social networks. Although there are established criteria and instruments assessing antisocial behavior there are few examining such behavior online. Therefore, the present study aimed to develop the Online Antisocial Personality Scale (OAPS). The OAPS was developed using the diagnostic criteria for antisocial personality disorder in DSM-5. The OAPS assesses antisocial behavior in online environments. The present study comprised 447 adolescents (219 girls and 228 boys) from four different samples. The measures used included the Online Antisocial Personality Scale (OAPS), E-Bullying Scale (E-BS), and Personality Belief Questionnaire-Short Form (PBQ-STF). The structural validity of OAPS was investigated with exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and criterion validity. When validity and reliability analysis of the OAPS are considered as a whole, it is concluded that the OAPS is a valid and reliable scale that assesses online antisocial personality among adolescents.