Asthma is a disease characterized by reversible bronchoconstriction, but some subjects develop fixed airflow obstruction (FAO). Subjects with FAO present more asthma symptoms and may have increased sedentary behavior; however, the effect of FAO on aerobic fitness and physical activity levels (PAL) remains poorly understood. Aim: To compare adolescents with asthma and FAO and adolescents with asthma without FAO in terms of aerobic fitness, PAL, muscle strength, and health-related quality of life (HRQoL). Methods: This cross-sectional study included adolescents with asthma, both sexes, and aged 12 to 18 years. They were divided into 2 groups: FAO and non-FAO groups. The adolescents were diagnosed with asthma in accordance with the Global Initiative for Asthma guidelines and underwent optimal pharmacological treatment for at least 12 months. FAO was diagnosed when FEV1/FVC ratio was below the lower limit of normal range after optimal treatment. Aerobic fitness, PAL, peripheral and respiratory muscle strength, and HRQoL were evaluated. Results: No significant differences were observed between FAO and non-FAO groups regarding the peak oxygen uptake (34.6±8.5 vs. 36.0±8.4 mLO2/min/kg), sedentary time (578±126 vs. 563±90 min/day), upper limb muscle strength (29.1±5.9 vs. 28.1±5.7 kgf), lower limb muscle strength (42.8±8.6 vs. 47.6±9.6 kgf), or HRQoL (5.1±1.3 vs. 4.7±1.4 score) (p>0.05). However, the FAO group exhibited a higher maximal expiratory pressure than did the non-FAO group (111.5±15.5 vs. 101.5±15.0 cmH2O, respectively). Conclusion: Our results suggest that FAO does not impair aerobic fitness, PAL, peripheral muscle strength, or HRQoL in adolescents with asthma. Furthermore, adolescents with asthma were physically deconditioned.