Background: Abnormal uterine bleeding is a bleeding from uterine compose that is abnormal in volume, regularity and/or timing that has been present for the majority of the last 6 months. Evaluation of women with abnormal uterine bleeding should comprise history taking, systemic and local examination, laboratory investigations, imaging and different diagnostic procedures including hysteroscopy. Aim of the Work: to assess the accuracy of hysteroscopy in the diagnosis of the cause of bleeding in women with abnormal uterine bleeding. Patients and Methods: This prospective observational study was conducted on 114 patients attended the Early Cancer Detection Unit, Faculty of Medicine, Ain Shams University between July 2017 and April 2018, to assess the role of diagnostic hysteroscopy and histopathology in evaluation of abnormal uterine bleeding. Results: Hysteroscopy had a sensitivity of 91.9%, specificity of 86.5%, positive predictive value of 93.2%, and negative predictive value of 84.2% and diagnostic accuracy of 90.1% for diagnosing the etiology of abnormal uterine bleeding. Conclusion: Hysteroscopy has a definitive role in evaluating patients with abnormal uterine bleeding especially with patient with thick endometrium, in any age group. Hysteroscopy is a safe and reliable procedure in the diagnosis of cases with abnormal uterine bleeding with high sensitivity, specificity, positive predictive value and negative predictive value and the results of hysteroscopy are immediately available. Hysteroscopy and histopathology complement each other in evaluating patients with abnormal uterine bleeding for accurate diagnosis and further treatment.