Infection with sexually transmitted diseases and unwanted pregnancies are risks associated with adolescents’ risky sexual behavior. Mental models of attachment relationships influence behavior and may influence adolescents’ involvement in sexual activities that are risky. This study explored whether attachment styles predicted adolescents’ involvement in risky sexual behavior. A correlational study design was adopted with 367 students from public secondary schools in Nairobi County taking part in the study. The Attachment Styles Questionnaire and Risky Sexual Behavior Scale were used to collect data. Multiple regression analysis was used to determine whether secure, preoccupied, dismissing or fearful attachment styles predicted students’ risky sexual behavior. The study found that preoccupied attachment style and secure attachment style had predictive effects on risky sexual behavior. Preoccupied attachment style was predictive of greater involvement in risky sexual behavior whereas secure attachment style was predictive of less risky sexual behavior. It was evident based on the findings that secure attachment style was protective against risky sexual behavior whereas preoccupied attachment style created vulnerability to risky sexual behavior. It was recommended that special attention should be paid to adolescents with insecure attachment styles in guidance and counseling programs aimed at discouraging adolescents’ risky sexual behavior and parents/guardians should be encouraged to be more nurturing towards their children in order to encourage formation of secure attachment which was protective against risky sexual behavior.