Abstract Uterine adenomatoid tumors are usually solitary lesions. Adenomatoid tumors diffusely infiltrating the entire myometrium have rarely been reported in the literature. A feature common to half of the reported cases of diffuse uterine adenomatoid tumor was an immunocompromised status of the patient caused by the medications for renal transplantation. In this article, we describe an unusual case of diffuse uterine adenomatoid tumor in a patient with chronic hepatitis C virus infection. Pelvic examination showed an irregular and enlarged uterus. Supracervical hysterectomy and bilateral salpingo-oophorectomy was performed with a clinical diagnosis of uterine leiomyoma. Pathological examination showed, in addition to multiple leiomyomas, diffuse uterine adenomatoid tumor. We suggested that the diffuse pattern in our patient might be related to immunosuppression secondary to chronic hepatitis C virus infection.