Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy, with poor survival rates among patients who have advanced disease despite recent significant advances in therapy, including therapy targeting the homologous recombination pathway. Evidence that cell-mediated antitumor immunity, as well as documented programmed death ligand 1 expression, is correlated with improved survival in EOC garnered early optimism regarding the utility of immune checkpoint blockade (ICB) in ovarian cancer. However, the results of multiple clinical trials investigating ICB have revealed very low levels of activity of single-agent immune checkpoint inhibitors, and the testing of combination therapies has not yet identified any combinations with robust activity in a significant proportion of patients who have EOC. In this review, we summarize the results of the major studies of ICB monotherapy and combinations; review novel combinations under investigation, including ICB with cellular therapies; and discuss potential candidate biomarkers for improving the selection of patients who may respond to ICB.