We report a non-invasive mixed mucin-producing and squamous differentiated tumor of the uterine cervix. This tumor was composed of two cell types: mucin-producing cells and non-mucin-producing cells. These cells were intimately mixed with each other, and showed intraepithelial spreading. The mucin-producing cells showed signet-ring or columnar shapes, and were localized to the lower-to-upper epithelial layer. The non-mucin-producing cells had eosinophilic cytoplasms with a monotonous appearance through the epithelium. Mitosis was sometimes observed in both cell types. Immunohistochemically, both cell types were positive for p16INK4A. The non-mucin-producing cells were positive for p63 and 34 beta E12, suggesting squamous differentiation. Although most mucin-producing cells were p63-, a few of them were p63+ and many 34 beta E12 immunoreactive cells were found in the mucin-producing cells. This tumor was adenosquamous carcinoma in situ.