Introduction: Malignant surface epithelial ovarian carcinomas usually present at an advanced stage of the disease and also one of the leading causes of cancer-related deaths in women despite multimodality treatment. Programmed death-ligand -1 (PDL-1) is a co-regulatory molecule expressed on the surface of ovarian tumour cells as well as immune cells, binds to its receptor programmed death receptor (PD-1) and suppresses the local tumour immunity thereby helping the tumour cells to spread and metastasize. Objective: To determine the immunohistochemical expression of PD L-1 in tumour cells and immune cells in malignant surface epithelial tumours of the ovary. To correlate the level of PDL-1 expression with histopathological parameters of surface epithelial tumours of the ovary. Methods: Immunohistochemical expression of PDL-1 in 100 cases of surface epithelial tumours of ovary were studied. Clinicopathological parameters, history of presurgical treatment, response to treatment, presence of tumour implants and presence of metastasis etc were obtained from the hospital medical records. The intensity and extent of membranous staining by anti-PD L-1 were scored for the tumoural cells and the tumour infiltrating immune cells separately. Statistical analysis was done on the data collected using the __ampersandsignldquo;SPSS Version 11__ampersandsignrdquo; statistical program. Pearson Chi-square test was used to determine significant clinicopathological differences between PD-L1 expression in positive and negative tumours. Results: PDL-1 expression in tumour cells was high in 6(6%) cases and 22(22%) cases showed expression in immune cells in tumour micro-environment. A significant statistical correlation between PDL-1 expression and grade and histological type of tumour was noted. Conclusion: High expression of PD-LI was noted in tumour infiltrating immune cells in more number of cases than that of the expression in tumour cells. The present study indicates that expression of PD-L1 is related to histologic type, the grade of the tumour and ovarian surface involvement by tumour cells with statistical significance.