We describe a case of synovial sarcoma of the larynx, and we discuss the use of fluorescence in situ hybridization (FISH) in confirming the diagnosis. The patient was a 21-year-old woman who presented with a recurrence of a previously resected supraglottic tumor of the aryepiglottic folds. A horizontal supraglottic laryngectomy was performed, and the 0.5-cm tumor was resected. Histopathologic study suggested that it was a biphasic malignant tumor compatible with a synovial sarcoma. The diagnosis of synovial sarcoma was confirmed by FISH immunohistochemistry with the use of an SYT break-apart probe. The patient recovered satisfactorily, but at follow-up 5 years and 4 months later, tumoral activity was evident in the left side of the neck. A biopsy found that 5 lymph nodes contained a metastasis of the synovial sarcoma. Again, a bilateral neck dissection was performed, and it revealed that 16 of 16 right-side nodes and 36 of 36 left-side nodes were negative. Two months later, the patient received 46 Gy of radiotherapy in 23 sessions. She remained free of disease during 2 more years of follow-up. Synovial sarcoma of the larynx is a rare entity. Organ preservation seems to be indicated in these cases. The histologic diagnosis may be difficult. In this case, the identification of a genetic mutation corroborated the diagnosis.