Obesity is associated with increased systemic and airway oxidative stress, which may result from a combination of adipokine imbalance, comorbidities, and reduced antioxidant defenses. While obesity-mediated increased oxidative stress plays an important role in the pathogenesis of vascular disease and nonalcoholic hepatic steatosis, little is known of how it may affect the lung. Contrary to what has previously been thought, the combination of obesity and asthma, both chronic inflammatory diseases, does not necessarily result in a synergistic effect, leading to even greater oxidative stress. However, most available studies have compared the levels of oxidative stress biomarkers on stable asthma patients, and it is possible that the interaction of oxidative stress between obesity and asthma is not readily detectable under basal conditions. We propose that obesity-mediated oxidative stress, which may affect the lung function of asthmatic subjects by increasing airway inflammation and reducing the effectiveness of inhaled corticosteroids, may become evident during exposure to an aggravating factor or during periods of asthma exacerbation. Understanding whether obesity-mediated oxidative stress has a mechanistic role in the association between obesity and asthma will help in the formation of public health policies and increase our capacity to develop therapeutic interventions that improve the life of obese asthmatic subjects.