Postmenopausal bleeding (PMB) with a diffusely enlarged uterus necessitates Magnetic Resonance Imaging (MRI) to reach an accurate diagnosis. Adenomyosis, especially extensive glandular variant, is an extremely rare cause reported in a postmenopausal woman. We present a challenging case of an 81-year-old woman with PMB where preoperative MRI suggested possible invasive endometrial neoplasm. However, final histopathological evidence of the hysterectomy specimen suggested Adenomyosis with extensive glandular proliferation. The patient was a multiparous lady with controlled diabetes and hypertension (controlled on medications) and a Body Mass Index of 36 kg/m