Mixed sex cord-stromal tumors (SCSTs) are rare neoplasms derived from or display differentiation towards primitive sex cords and stromal cells. The 2020 World Health Organization classification of mixed SCSTs included Sertoli-Leydig cell tumor (SLCT), SCST, not otherwise specified (NOS), and gynandroblastoma in this category. This chapter highlights the clinicopathologic characteristics, advances in molecular features, a detailed discussion of differential diagnostic considerations, the utility and limitations of immunohistochemical markers, and ancillary studies in their diagnostic work-up.