Ovarian cancer is the second leading cause of cancer-related mortality among gynaecological cancers in the Western world. Although initial responses to 1st line treatment are high, over 75% of patients eventually relapse and acquire chemotherapy resistance, which is the primary cause of ovarian cancer treatment failure. New therapies against ovarian cancer to improve patient outcomes are therefore urgently required. Chimeric antigen receptor T (CAR-T) cell therapy is adoptive immunotherapy that is currently being used to treat some blood cancers. CAR-T cell therapies have so far been less effective against solid cancers, due in part to the absence of suitable tumour-associated antigen (TAA). This study has investigated whether Leucine-rich repeat-containing G protein-coupled receptor 5, LGR5) is a suitable target for CAR-T cell therapy for ovarian cancer. We found that LGR5 is highly expressed in HGSOC cancer lines (COV318, COV362 and OAW28) and increased in HGSOC tissues following relapse with the chemotherapy-resistant disease. We assessed the cytotoxic effects of LGR5-CAR-T cells on a range of ovarian cancer cell lines and primary serous ovarian cancer cells derived from patient ascites in vitro by MTT and 3D spheroid assays. We demonstrated that LGR5-CAR-T cells were cytotoxic and significantly inhibited the survival of ovarian cancer cell lines (COV318, COV362) that express high levels of LGR5 but not SKOV3 or OV90 that express lower LGR5 levels in monolayer culture. In addition, LGR5-CAR-T cells were cytotoxic and significantly inhibited the survival of primary serous ovarian cancer cells compared to un-transduced CD3+ T cells. LGR5 CAR-T cells also exhibited anti-tumour activity against ovarian cancer cell lines (COV318, COV362 & OAW28) and primary serous ovarian cancer cells in vitro using 3D-spheroid culture assays. This study demonstrates that LGR5-CAR-T cells have great potential to be developed as a novel immunotherapy for ovarian cancer.