Suicide is the leading cause of death among South Korean adolescents. The purpose of this study was to examine the relationship between suicidal thoughts (ST) and suicidal attempts (SA) with the level of physical activity (PA) among South Korean adolescents. Based on data from the eighth Korea Youth Risk Behaviors Web-Based Survey, 74,186 South Korean adolescents were evaluated in terms of their relationship between meeting guidelines for vigorous PA (VPA), moderate PA (MPA), and low PA (LPA) and in respect of ST and SA status. The adjusted odds ratio in adolescents who thought about suicide increased significantly with PA levels (1.02 in males, 1.21 in females with VPA, 1.10 in males, 1.18 in females with MPA, and 1.16 in males, 1.20 in females with LPA) compared to participants who did not think about suicide. In addition, the AOR in adolescents who attempted suicide increased significantly with PA levels (1.16 in males, 1.36 in females with VPA, 1.13 in males, 1.15 in females with MPA, and 1.26 in males, 1.15 in females with LPA) compared to participants who did not attempt suicide. These results show that VPA, MPA, and LPA are positively associated with ST and SA prevention in South Korean adolescents. Therefore, to prevent suicide of South Korean adolescents, we support public health program including PA participation.

• South Korean male adolescents, compared to female adolescents, showed relatively high values for physical activity-related variables such as vigorous, moderate, and low PA.

• Regardless of gender, more physical activity participation is positively associated with prevention of suicidal thought and attempts of South Korean adolescents.

• To prevent suicide of South Korean adolescents, we support public health program including meeting guidelines for vigorous, moderate, and low physical activity.