Patients with Cornelia de Lange syndrome have many anomalies including micrognathia with a small mouth, a high arched palate, and a short neck, which might make laryngoscopy for tracheal intubation difficult during induction of general anesthesia. General anesthesia was performed in a patient with Cornelia de Lange syndrome, and restricted opening of the mouth, which had not been reported previously, was found during laryngoscopy. The possible causes were thought to be temporo-mandibular joint disorders, contracture of the masseter muscle due to injury by self-destructive tendencies, or elogated coronoid process. The potential difficulty with laryngoscopy should be considered for tracheal intubation in a patient with Cornelia de Lange syndrome.