Background: Abnormal uterine bleeding (AUB) in perimenopausal women may indicate a spectrum of endometrial pathology ranging from atrophic change to carcinoma, and transvaginal sonographic measurement of endometrial thickness (ET) has been proposed as a non-invasive tool to triage women who require histopathological sampling. This study aimed to determine the distribution of ET and histopathological diagnoses among perimenopausal women with AUB and to evaluate the diagnostic performance of ET cut-off values in predicting endometrial pathology. Materials & Methods: This cross-sectional study was conducted in the Department of Radiology and Imaging, Sylhet MAG Osmani Medical College Hospital, Bangladesh, in collaboration with the Departments of Obstetrics and Gynaecology and Pathology, from July 2021 to June 2023. Ninety-seven perimenopausal women aged 39 years and above presenting with AUB underwent transvaginal sonography followed by histopathological evaluation of endometrial samples. ET was correlated with histopathological findings using the chi-square test. Results: The mean age was 43.04±2.54 years; menorrhagia was the commonest symptom (51.5%). The overall mean ET was 7.98±3.32 mm, ranging from 5.83±1.06 mm in atrophic endometrium to 12.15±2.36 mm in endometrial polyps. ET was significantly associated with histopathological diagnosis (χ²=21.74, p<0.001). An ET cut-off of >4.9 mm gave 100% sensitivity and negative predictive value but 24.0% specificity; >7.9 mm gave the best balance (66.0% sensitivity, 76.0% specificity, 71.1% accuracy); >11.9 mm gave 100% specificity and positive predictive value but 29.8% sensitivity. Conclusion: Endometrial thickness correlates significantly with histopathological diagnosis in perimenopausal women with AUB. No single cut-off simultaneously optimises both rule-in and rule-out performance; a graded diagnostic approach combining ET with clinical judgement is recommended before proceeding to invasive sampling.