Objective: To examine differences in depressive and anxiety symptoms between boarding and non boarding high school students and their associations with physical activity (PA) patterns, so as to provide evidence to inform adolescent mental health promotion. Methods: From October to December 2024, a convenience sample of 11 782 students aged 15-18 years was recruited from 36 schools in Nanchang, Ganzhou, and Shangrao of Jiangxi Province. Depressive and anxiety symptoms and PA were assessed using the Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and International Physical Activity Questionary Short Form (IPAQ-SF). Logistic regression model was used to examine associations between PA patterns, depressive and anxiety symptoms among boarding and non boarding students. Results: The detection rates of depressive symptoms were 45.7% and 46.4% among boarding and non boarding students, respectively; for anxiety symptoms, the corresponding rates were 43.0% and 46.7%. Boarding and non boarding students differed significantly in smoking status, screen time, sleep duration, sedentary time, daily vegetable intake, and napping ( χ 2=16.74-664.17, all P <0.01). Across PA pattern groups, the detection rates of depressive and anxiety symptoms differed significantly between boarding and non boarding students ( χ 2 depression = 23.85 , χ 2 anxiety = 22.78, both P <0.01). Adjusted for confounding factors, Logistic regression analysis of high school students showed that compared with the not meeting PA recommendations, both the concentrated and regular PA pattern were associated with lower odds of depressive symptoms [ OR (95% CI )=0.83(0.70-0.98), 0.90(0.83-0.98)]; and the concentrated pattern was also associated with lower odds of anxiety symptoms [ OR (95% CI )=0.78(0.65-0.92)], and the association of anxiety symptoms in concentrated boarding students was consistent with that of the overall group [ OR (95% CI )=0.71(0.52-0.98)] (all P <0.05). Conclusions There is a correlation of different physical activity patterns with depressive and anxiety symptoms among boarding and non boarding high school students. Schools should ensure students engage in regular physical activity and work to increase overall activity volume.