The Tri-Border Region has several social and health problems among young people, however, there are no data about the overweight between adolescents. This study investigated the prevalence of overweight and associated factors in students from Tri-Border Region: Argentina, Brazil and Paraguay. Study participants were 1.183 students, ages from 15 to 18 years. The overweight was identified according to body mass index cut-off points proposed by the World Health Organization. The Global School-Based Student Health Survey questionnaire was used to identify sociodemographic (gender and age) and behavioral factors (physical activity outside of school, commuting to school, time watching TV and fruits, vegetables, sweet, and salty snack consumption) associated with overweight in adolescents. It was used the descriptive statistics, analysis of variance, chi-square and binary logistic regression, adopting p < 0.05. Thirteen percent of students were overweight. Boys were approximately two times more likely to have overweight than girls, independently of nationality. Brazilian students that realized passive commuting to school and Argentineans students with low consumption of vegetables (< 1 time/day) were 2.2 and 2.9 times more likely to have overweight than their counterparts who performed active commuting to school and consumed vegetables daily, respectively. These results suggest that public policies to combat overweight should attention on promoting healthy lifestyle among young people from Tri-Border Region.