Background: Adnexal mass is a common presentation in today’s gynecological practice. The incidence of ovarian cancer is increasing day by day and diagnosis is often difficult to be made pre operatively with inadequate surgical exploration is a regular occurrence. Aims and Objectives: To assess and validate the importance of RMI-3 score as pre-operative diagnostic tool of differentiating benign from malignant adnexal mass for starting first line therapy of ovarian cancer and to find out the incidences of ovarian malignancy among study population. Material and Methods: The study was conducted in the Department of Gynecology and Obstetrics on (n=115) patients attending GOPD and indoor with adnexal mass fulfilling the inclusion and exclusion criteria using purposive sampling technique. All the selected cases underwent ultrasonography and serum CA- 125 level estimation necessary for calculating RMI score. A score of >200 was taken as suggestive of malignancy and confirmatory diagnosis was performed by histopathological examination obtained from staging laparotomy of adnexal mass. The individual scores were then correlated with final outcomes with statistical analyses. Results: The study revealed benign ovarian tumors are more under 50 years (78.46%) and patients with normal BMI are diagnosed with maximum of malignancy (n = 28). History of tubal ligation carried less risk of malignancy (p200) had more efficacy than serum CA-125 level (>46) in differentiating malignant lesions from benign one in terms of specificity (96% vs 83.87%) and positive predictive value (95% vs 79.17%). Conclusions: RMI-3 score is a simple, reliable and effective tool in differentiating benign from malignant adnexal masses thereby help in quick referral and management of cases with increase chances of survival of the patients.