The aim of this paper is to examine the role of physical education (PE) teacher and classmate support in relation to sex and BMI status in adolescents' physical activity (PA) in Kosovo. A Classmate and Teacher Support Scale (with additional questions) was used on a cross-sectional sample of 608 girls and 620 boys aged 15-18, randomly selected from secondary schools of seven major municipalities in Kosovo. PA level was determined with a Physical Activity Screening Measure questionnaire. Descriptive statistics and a three-way ANOVA, along with Tukey's HSD post hoc test, were employed. The findings showed the levels of teacher and classmate support to be important factors in stimulating adolescents' PA. It was found that boys with normal weight, high support from teachers, and medium or high support from classmates were more physically active, compared with girls.