Serous neoplasms of the ovary are composed of tumors where the epithelial cell type resembles that of the fallopian tube. These tumors range from benign, borderline to frankly malignant. Our understanding of borderline and malignant serous neoplasms has evolved in the past few decades. Serous borderline tumor (SBTs), though uncommon, are encountered in routine practice and have been the subject of several controversies regarding terminology and diagnostic criteria, which will be addressed. Our understanding of the pathogenesis of ovarian cancer has advanced significantly, but controversy still exists regarding its origin, and recent studies have suggested the possibility of origin in the fallopian tube, at least in a subset of cases. Approximately 10% of ovarian cancers are hereditary due to mutations in the BRCA1 or BRCA2 genes, which not only poses one of the strongest risk factors but also has implications for patients and family members in terms of risk-reducing surgery options. From a practical standpoint, familiarity with the diagnostic criteria of high- and low-grade serous carcinoma is necessary for pathologists. This chapter addresses the pathologic features, relevant immunohistochemistry, molecular genetics, and challenges associated with the diagnosis of ovarian serous neoplasms.