Objectives The purpose of this study was to explore the factors affecting adolescent suicide risk and to compare middle and high school students as a basis for developing targeted programs. Methods Based on the results of the safety perception survey of 527 adolescents in Ilgae-gun, Chungcheongnam-do, relevant variables were measured and used in the analysis. The suicide risk for individual system, environmental system, and social system factors were analyzed using t-test and analysis of variance. Hierarchical regression analysis was used to compare the risk factors in Model 1, Model 2, and Model 3. Results The risk factors for suicide among adolescents that included individual, environmental, and social system factors were depression, school maladjustment, experience of sexual violence, and experience of being victimized by violence. In middle school students, depression, sexual violence, victimization, and school maladjustment were the most important risk factors for suicide, followed by negative relationships with teachers. For high school students, depression, victimization of violence, school maladjustment, victimization of sexual violence, and negative peer relationships, in that order, and perpetration of school violence were negative predictors of suicide risk. Conclusions The environment and social relationships are more influential than individual deviance as risk factors for suicide in youth. Depression and sexual victimization were major risk factors for both middle and high school students, but were particularly strong in middle school. In high school, relationship conflicts at school were identified as a major risk factor for suicide, with victimization of school violence and school maladjustment being high, along with negative peer relationships. As sexual violence factors were high risk factors in both middle and high school students, it is suggested that gender sensitivity education for adolescents is necessary.