The cysteinyl leukotrienes cause bronchoconstriction, increased mucus production and airway inflammation, three major features of asthma. Several randomized controlled trials have shown the efficacy of leukotriene receptor antagonists for improving asthma outcomes. The drug is favored for treating childhood asthma, where poor compliance with inhalation therapy is a therapeutic challenge. To assess the effectiveness of Montelukast in asthmatic children under real-life conditions, a prospective, single-arm, multicenter, open-label observational study was performed on asthmatic children 2- to 14-years-old with a history of physician-diagnosed mild persistent asthma. Montelukast was given once daily for 12 consecutive weeks. By the end a significant improvement of the daytime asthma symptom score, nighttime asthma score, peak expiratory flow rate (PEFR) and mean score of the investigators' global evaluation was noted (p < 0.05). These results suggest that montelukast is an effective monotherapy controller in children with mild persistent asthma.