Tonsillectomy is one of the most common operations performed by otolaryngologists. Fever, otalgia, dehydration, sore throat, and hemorrhage are common complications. In this clinical report, a 7-year-old boy was presented with a synechia between the posterior plicae together with recurrence of adenoid hypertrophy after adenotonsillectomy 1 year previously. The synechia and adenoid were resected, and the patient was discharged from the hospital after 2 days. The complication in this case was most likely caused by traumatic injury of the posterior plicae during the previous tonsillectomy. This complication is, however, very rare.