Background & Objectives:Serous ovarian carcinoma (SOC) is characterized by extreme genomic instability, chromosomal rearrangements and copy number variations (CNVs) leading to the development of early metastasis and chemo-resistance. The present study was designed to observe the role of CNVs of Cyclin E1 (CCNE1) and Epithelial cell transforming sequence- 2(ECT2)genes and their encoded proteins in predicting the chemotherapeutic response in SOC patients.Methods:This observational analytical study was conducted at University of Health Sciences, Lahore, Pakistan from December 2019 till June 2022.The study included twenty-five SOC patients with resectable ovarian tumors and twenty-five control subjects. The patients were followed-up for six months for their response to chemotherapy. The CNVs inCCNE1andECT-2genes were determined by real time PCR while serum levels of encoded proteins were determined in controls and cases, before and after six months of treatment, through ELISA. The response to chemotherapy was categorized as sensitive or resistant based on serum CA-125 levels and radiological scans.Results:The copy number variations inCCNE1andECT2 genesshowed association with the clinic-pathological characteristics and chemotherapy response. Statistically significant difference was found between the mean pre-chemotherapy protein levels ofCCNE1in cases than controls (p-value <0.001) and between the mean pre and post-chemotherapy protein levels ofCCNE1 and ECT2 (p-value <0.001) in SOC patients.Conclusion:The copy number variations ofCCNE1andECT2 genesand their protein expression are positively associated with chemotherapeutic response in SOC patients.