Mucinous neoplasms of the ovary may have associated benign or malignant mural nodules. A leiomyomatous mural nodule is a rare, benign lesion associated with mucinous tumors of the ovary. We report a case of a mural leiomyomatous nodule arising in a benign mucinous cystadenoma in a 29-year-old woman who presented with a large heterogenous abdominal mass. After pre-operative evaluation, exploratory laparotomy was performed upon suspicion of ovarian malignancy. A pathological examination confirmed the benign nature of the mural nodule.