Abstract Objectives: The present study aimed to identify the prevalence of incest among Korean adolescents and to determine the family problems, perceived family dynamics, and psychological consequences associated with incest in South Korea. Design: A cross-sectional study was performed, using an anonymous, self-reporting questionnaire. Data were analyzed by percentages, Chi-square, and t-test statistical analyses, using SAS software program. Sample: A total of 1,672 adolescents (1,053 student adolescents and 619 delinquent adolescents) were selected using proportional stratified random sampling method in this study. Results: The results showed a 3.7% prevalence of incest in the tested Korean population. Families in which incest occurred were characterized by higher levels of problems, such as psychotic disorders, depression, criminal acts, and alcoholism among family members. Adolescent incest victims showed significantly more dysfunctional and unhealthy in terms of family dynamics and expressed significantly higher maladaptive and problematic psychological patterns than nonvictimized adolescents. Conclusions: The present findings identified some of the family problems and dysfunctional family dynamics may associate with intrafamilial child sexual abuse in Korea. Therefore, when an allegation of intrafamilial sexual abuse is made, health professionals should carry out a comprehensive assessment of their family dynamics and an evaluation of the impact of the abuse on the child and family.