Background: Aerobic fitness and body adiposity are important health markers that should be encouraged to improve the lifestyle and general health of adolescents. The aim of the study was to compare body adiposity and aerobic fitness of Brazilian and Chilean adolescents from public schools. Methods: A descriptive (comparative) study was developed in adolescents attending public schools in a region of Brazil and Chile. The age range of the students was 14 to 17 years. Two schools located in the urban area of Campinas (Brazil) and Talca (Chile) were selected. Weight, height and aerobic fitness (20 m round-trip test) were evaluated. VO2max (ml/kg-1/min-1) and body mass index (BMI) were calculated. Nutritional status was classified by BMI. Results: In men, the average age of Chilean adolescents was 15.41 ± 0.75 years, BMI was 22.79 ± 3.58 kg/m2 and aerobic fitness was 44.1 ± 6.6 ml/kg-1/min-1. In Brazilian adolescents, age was 14.78 ± 0.64 years, BMI was 21.90 ± 4.59 kg/m2 and aerobic fitness was 41.8 ± 6.3 ml/kg-1/min-1. In women, the average age in Chilean women was 15.40 ± 0.75 years, BMI was 22.80 ± 3.58 kg/m2 and aerobic fitness was 36.8 ± 4.3 kg/m2. In Brazilian women, age was 14.80 ± 0.64 years, BMI was 21.90 ± 4.88 kg/m2 and aerobic fitness was 37.0 ± 3.6 ml/kg-1/min-1. The relationships between body adiposity and aerobic fitness in both sexes and countries ranged from (R= -0.32 to - 0.41). Conclusions: No differences were observed in body adiposity and aerobic fitness between adolescents from Chile and Brazil, moreover, it was determined that adolescents classified as normal weight, reflected a higher aerobic fitness than their peers with excess body weight.