Objective: To determine the frequency and histological types of malignant ovarian tumours using morphological features and immunohistochemistry. Study Design: Cross-sectional study. Place and Duration of Study: Department of Histopathology, Army Medical College, Rawalpindi Pakistan, Jan 2016 to Dec 2018. Methodology: Newly diagnosed cases of malignant ovarian tumour who had not received chemotherapy were included. Cases of benign ovarian tumours and those who were treated with pre-surgical chemotherapy were excluded. Results: In total, 118 cases of malignant ovarian tumours were evaluated. High-grade serous carcinomas were 61(51.7%), which outnumber others, followed by granulosa cell tumours 17(14.4%), germ cell tumours 13(11%), endometrioid carcinoma 9(7.6%), clear cell carcinoma 4(3.4%), mucinous carcinoma 4(3.4%), low-grade serous carcinoma 2(1.7%) and carcinosarcoma in one case (0.8%). Cancer in the ovary was metastatic in 7(5.9%) cases. No Sertoli Leydig cell tumour, malignant Brenner tumour, embryonal carcinoma or immature teratomas were diagnosed. Conclusion: Surface epithelial tumours were the most common malignancy, followed by granulosa cell tumours and dysgerminoma. An increase in the frequency of ovarian tumours in younger age groups was also noted. Immunohistochemistry was a useful adjuvant diagnostic tool in cases of ovarian malignancy. Metastases to the ovary were mostly gastrointestinal in origin.