Intimate partners and other informal caregivers provide unpaid tangible, emotional, and decision-making support for patients with cancer, but relatively little research has investigated the cancer experiences of sexual minority women (SMW) with cancer and their partners/caregivers. This review addressed 4 central questions: 1) What social support do SMW with cancer receive from partners/caregivers? 2) What effect does cancer have on intimate partnerships or caregiving relationships of SMW with cancer? 3) What effects does cancer have on partners/caregivers of SMW with cancer? 4) What interventions exist to support partners/caregivers of SMW or to strengthen the patient-caregiver relationship? This systematic review, conducted in 2018 and updated in 2020, was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two independent coders screened abstracts and articles. In total, 550 unique records were screened; 42 articles were assessed for eligibility, and 18 were included in a qualitative synthesis. Most studies were U.S.-based, involved breast cancer, included intimate partners, had primarily white/Caucasian samples, and were cross-sectional. Sexual minority female participants reported that partners/caregivers often provide important social support, including emotional support, decision-making support, and tangible support. Effects of cancer on relationships with partners/caregivers were mixed, with some studies finding relationships remained stable and others finding cancer either increased closeness or disrupted relationships. Participants reported partners/caregivers often experience distress and may experience discrimination, discomfort disclosing sexual orientation, and a lack of sexual minority-friendly services. No studies involved an intervention targeting partners/caregivers or the dyadic relationship. More work is needed to understand SMW with cancers other than breast cancer, and future work should include more racially, ethnically, and economically diverse samples. Longitudinal research will allow an examination of patterns of mutual influence and change in relationships. These steps will enable the development of interventions to support SMW with cancer and people close to them. • This review synthesized 18 articles about sexual minority women and cancer. • Partners/caregivers often provide crucial social support to sexual minority women. • Effects of cancer on relationships with partners/caregivers were mixed. • Partners/caregivers may experience distress and discrimination. • More work is needed in diverse samples and in cancers other than breast cancer.