Atypical polypoid adenomyoma (APA) is an uncommon type of polypoid characterized by fibroid stroma and endometrial glands. It occurs mostly in premenopausal women and rarely in postmenopausal women with irregular vaginal bleeding. In our current case, a 76-year-old woman presented with irregular vaginal bleeding. The final pathological diagnosis of the mass was APA. APA is not easy to diagnose before surgery. On the one hand, there was no obvious particularity in imaging features and clinical features, especially for uncomfortably identifying endometrial cancer. On the other hand, APA has a pedicle, attaching to any part of the uterine cavity, which can cause pseudocoel between the mass with the uterine cavity wall. So, when it comes to getting the pathological tissue in the absence of hysteroscopy, it is easy to access to the pseudocoel and obtain endometrial tissue rather than the pathological tissue of the mass. Therefore, preoperative imaging examination is of great significance diagnosis way of thinking to clinicians for APA. In the meantime, pathological tissue of APA can be obtained by hysteroscopy in visual conditions.