A 46-year-old woman presented with increasing abdominal girth. Investigations revealed bilateral ovarian tumors but no evidence of systemic disease. A total abdominal hysterectomy and bilateral salpingo-oophorectomy were performed. There was no evidence of extraovarian tumor at the time of the operation. A diagnosis of precursor B cell lymphoblastic lymphoma was established by histologic examination, immunohistochemical staining, and molecular analysis. After a 6-month follow-up, there was evidence of focal bony involvement that improved after chemotherapy. Although non-Hodgkin's lymphoma may involve the female genital tract, particularly the ovaries, primary ovarian lymphoma is rare and its definition controversial. To the best of our knowledge, this is only the third reported case of a primary lymphoblastic lymphoma of the ovary.