We report the case of a rare association between achalasia and Down syndrome in a child presenting with symptoms that suggest a gastroesophageal reflux. Evaluation of the patient with 24-hour multichannel intraluminal impedance and pH recording and upper endoscopy lead to the diagnosis of achalasia. However, the persistence of the symptoms after the concurrent surgical myomectomy and fundoplication has led to repeat pH-impedance monitoring testing and endoscopy, which identified the presence of gastroesophageal reflux disease. We emphasize in this paper the importance of multichannel intraluminal impedance and pH monitoring in detecting esophageal motility disorders.