This study aims to see the contribution of loneliness to cybersex behavior in adolescents. The hypothesis test used was simple linear regression analysis with 150 subjects aged 15-21 years, which were determined by snowball sampling technique. The measuring instruments used were the Cybersex Scale and the Loneliness Scale compiled by researchers based on aspects of Delmonico & Miller (2003) and Russell (1996). This study found that loneliness contributes significantly to cybersex with an R Square value of 0.090, which indicates that loneliness makes an effective contribution of 9% to cybersex behavior in adolescents.