Seminal vesicle cysts are uncommon abnormalities in the pelvis. The case of a seminal vesicle cyst that extended through the inguinal canal is reported. A 35-year-old man presented with left inguinal swelling. He was diagnosed with a left inguinal hernia. However, the interpretative diagnosis was a spermatic cord tumor. The operation was changed to tumor resection. The tumor existed along with the vas deferens from part of the parietal peritoneum outside the inguinal tunnel to the deep pelvic space. The cylinder-shaped tumor was 3 cm in diameter and 20 cm long. Pathological examination revealed a seminal vesicle cyst that extended through the inguinal canal. To the best of our knowledge, this is the first case report of a seminal vesicle cyst inguinal hernia.