The purpose of this study was to identify the impact of pornography use among adolescents on their subsequent violent sexual behavior, and to ascertain the moderating effect of family support. The study was conducted with a sample of 2,087 Korean middle and high-school students. To analyze the data, a descriptive analysis, a correlation analysis, and a Poisson regression were conducted using SPSS 24.0. A Poisson regression was performed because the dependent variable, violent sexual behavior, was measured by the frequency of occurrence, and most responses were distributed at '0', indicating a non-normal distribution. The results indicated that 8.1% of adolescents admitted to having sexually violent experiences over the past year, with a relatively high rate of sexual harassment. Secondly, 53.3% of adolescents had used pornography over the past couple of years, with the highest percentage of use occurring via the Internet. Finally, pornography use among adolescents had a significant and direct impact on their sexually violent behavior, with family support playing a moderating role. This indicated that, for adolescents with a high level of family support, the impact of pornography usage on sexually violent behavior decreased. Based on these results, we discuss practical and policy interventions to prevent sexually violent behavior by adolescents.