A case of endometrial ossification in a 62 year old woman is reported. The patient presented with increased vaginal discharge. On transvaginal ultrasonography, a hyperechoic area within the uterine cavity, suggestive of an intrauterine foreign body, was noted. Histological examination of the endometrial curettage showed mature bone with neutrophilic infiltration. There was no evidence of malignancy. Endometrial ossification in postmenopausal women is very rare; most women presenting with this condition are between 20 and 40 years of age. Therefore, clinicians should consider the possibility of endometrial ossification as a differential diagnosis of intrauterine foreign body on ultrasound, even in older patients. In addition, pathologists should be aware of this rare entity to avoid a misdiagnosis of malignant mixed müllerian tumor in the endometrial curettage specimen, which may result in unnecessary hysterectomy.