Leiomyomatosis peritonealis disseminata (LPD) is a rare entity that is characterized by the presence of multiple subperitoneal or peritoneal smooth muscle nodules throughout the peritoneal surface mimicking a malignant process. LPD follows a benign course in general, and it is often found incidentally during abdominal surgery. There have been reported cases of LPD with malignant degeneration although the association is uncertain. Concurrent finding of LPD and leiomyosarcoma of the pelvis is very rare that could be coincidental, malignant transformation of LPD to leiomyosarcoma, or progression of undetected primary leiomyosarcoma. There are only a few previously reported cases in the literature. Herein, we report a case of 56-year-old woman with a history of leiomyoma of uterus who presented with progressive abdominal swelling secondary to mass lesions in the pelvis. The patient underwent exploratory laparotomy and debulking of the tumors, and the histologic examination of the tumors revealed coexistence of LPD and leiomyosarcoma. After recovery from the operation, core needle biopsy of the superficial, residual liver mass was obtained to investigate potential liver metastasis, and the histopathologic findings are consistent with leiomyoma which represents the first simultaneous occurrence of LPD, leiomyosarcoma, and leiomyomatous nodule of the liver.