Introduction: Adenotonsillar hypertrophy (AH) is considered the most common cause of upper respiratory tract obstruction among children. It results in a spectrum of symptoms from mouth breathing, nasal obstruction, hyponasal speech, snoring, and obstructive sleep apnea (OSA) to growth failure and cardiovascular morbidity. Adenotonsillectomy is a typical strategy for patients with AH, but may lead to serious complications such as bleeding (4–5%) and postoperative respiratory compromise (27%), especially among young children, as well as recurrence of adenoid tissue (10–20%). Thus, non-surgical therapies have attracted considerable attention as an alternative strategy. The inflammatory mechanism proposed for AH has lead to the use of anti-inflammatory drugs to manage this condition. The present study aimed to evaluate the effect of chewable tablets of montelukast, a cysteinyl- leukotriene receptor antagonist, in children with AH.   Materials and Methods: Sixty children between the ages of 4–12 years with >75% choanal obstruction on primary nasal endoscopy were recruited in this randomized, placebo-controlled trial and randomly divided into two groups. The study group was treated with montelukast 5 mg daily for 12 weeks while the control group received matching placebo for the same period of time. A questionnaire was completed by each child’s parent/guardian to assess the severity of sleep discomfort, snoring, and mouth breathing before and after the intervention.   Results: Adenoid size decreased in 76% of the study group compared with 3% of the placebo group after 12 weeks. A statically significant improvement was observed in the study group compared with the placebo group in terms of sleep discomfort, snoring, and mouth breathing. The symptoms average total score dropped from 7.7 to 3.3 in the study group, while in the placebo group the total score changed from 7.4 to 6.7.   Conclusion:  Montelukast chewable tablets achieved a significant reduction in adenoid size and improved the related clinical symptoms of AH and can therefore be considered an effective alternative to surgical treatment in children with adenoid hypertrophy.