The association between in utero diethylstilbestrol (DES) exposure and the development of clear-cell adenocarcinoma of the vagina and cervix has been well described. However, non-clear-cell mucin-secreting adenocarcinoma in women with DES exposure has not been previously reported. We present two cases of non-clear-cell mucinous adenocarcinoma in women having a history of in utero DES exposure. These cancers were found in older women and were more advanced than the clear-cell adenocarcinoma associated with DES. Histologic features of these tumors were notable for atypical, irregular glands lined by endocervical, intestinal, and endometrioid epithelium. The development of non-clear-cell adenocarcinoma of the vagina in these patients may be associated with DES exposure in utero. Long-term surveillance of DES-exposed women may be warranted.