Abstract Introduction/Objective Alveolar rhabdomyosarcoma is an aggressive tumor of skeletal muscle differentiation that predominantly affects adolescents and young adults, and is rare over 45 years of age. It has poor prognosis with metastasis, and most commonly spreads to the lymph nodes, bone marrow, and lungs. In this report, we describe a middle-aged patient with a primary sinonasal alveolar rhabdomyosarcoma which metastasized to the right testicle, an unusual metastatic site reported only a few times in literature. Methods/Case Report Our patient is a 53 year old male who presented in 2020 with recurrent epistaxis and bilateral cervical lymphadenopathy over a 2 month period. Maxillofacial CT/MRI imaging revealed a 4-cm sized mass within the left nasal cavity eroding into the ethmoid sinuses. The patient underwent endoscopic sinus surgery of the sinonasal mass, which on histology, appeared as poorly differentiated small round blue cells with numerous mitoses infiltrating as single cells and nests. These cells stained positive for vimentin, myogenin, desmin, and CD56, and negative for AE1/AE3, chromogranin, S-100, CD99, and CD45. The cells showed very high Ki67 proliferation index (70-80%) and tested positive for FOXO1 gene rearrangement, which supported the diagnosis of alveolar rhabdomyosarcoma. The patient completed chemoradiation therapy, and MRI scans over the next 2 years were negative for residual sinonasal tumor. However, the patient returned in 2022 after having undergone a right orchiectomy at an outside hospital for testicular pain, and abdominal CT showed diffuse retroperitoneal lymphadenopathy concerning for metastasis. On histology, the resected testicle showed seminiferous tubules infiltrated and destroyed by sheets of poorly differentiated small round blue cells with fibrous septae separating the nests of tumor cells into alveolar-like spaces with central loss of cohesion. The tumor cells showed the same immunohistochemical staining pattern as the primary sinonasal lesion, thus confirming it to be metastatic alveolar rhabdomyosarcoma. Results (if a Case Study enter NA) NA. Conclusion It is unusual for alveolar rhabdomyosarcomas to occur in adults over 45 years old, and is even rarer for these tumors to metastasize to the testicle. Metastases also only account for 1% of testicular tumors. Our report documents a very rare case of an alveolar rhabdomyosarcoma in a middle-aged adult which metastasized to the testicle after chemoradiation therapy.