Myeloid sarcoma is a rare extramedullary tumor often associated with acute myeloid leukemia (AML), but it can also appear as an isolated lesion. Vaginal involvement is extremely rare and may lead to delayed diagnosis due to nonspecific symptoms. We report a 41-year-old woman with a history of two cesarean sections who presented with dyspareunia. A firm, fixed mass was palpated on the posterior vaginal wall. Transvaginal ultrasonography and pelvic MRI revealed a 7.5 × 4.3 cm mass in the rectovaginal space without rectal infiltration. The lesion was excised vaginally, and intraoperative endoscopy confirmed rectal integrity. Histopathology showed blast cell infiltration with strong CD7, CD38, CD43, CD45, and BCL-2 positivity, consistent with myeloid sarcoma. Bone marrow biopsy confirmed AML. The patient was treated with 16 cycles of chemotherapy and underwent allogeneic bone marrow transplantation. This case illustrates the diagnostic challenge of vaginal myeloid sarcoma and emphasizes the role of imaging, immunohistochemistry, and multidisciplinary management in such rare presentations.