A peritonsillar abscess is a common deep infection that is usually related to acute tonsillitis. Needle aspiration is often performed for diagnosis and treatment, but several complications, including puncture of the carotid artery, may occur, even when performed by properly trained physicians. The utility of transoral pharyngeal ultrasonography (TOPU) equipped with a biopsy adaptor for safe and full aspiration is presented. A 19-year-old man was admitted to our hospital because of a peritonsillar abscess. TOPU showed the abscess and a branch of the carotid artery, and an otolaryngologist performed puncture through the biopsy adaptor with the aid of the ultrasound image. Needle aspiration was accomplished by avoiding arterial puncture and monitoring the shrinkage of the abscess. TOPU-guided needle aspiration is useful in the safe drainage of peritonsillar abscesses.