Objective: To clarify how breast cancer patients undergoing post-surgical hormone therapy cope with changes in their sexual lives and support themselves and their partners during these changes. Methods: Participants were 37 breast cancer patients undergoing post-surgical hormone therapy and attending mammary outpatient clinics. In-depth interviews and grounded theory were used to collect and analyze data, respectively. Results: First, sexual life was divided into four groups: "No complaint" regarding sexual activity, "Slight discord", "Handicapped in meeting a life partner" and "Uninterested" in sexual activity. Sexual life during surgical-hormone therapy did not change significantly from sexual life before breast cancer. Second, meanings of sexual activity for breast cancer patients were divided into five, "Regaining femininity", "Confirming love", "Sharing pleasure", "Response to partner's higher desire" and "Procreation". They differed by group. Third, coping strategies were divided into six, "Virtuous cycle to confirm love and regain lost femininity", "Struggle to avoid relationship crisis", "Reconfirmation of partner's affection by his abstinence", "Attempt to recover the sexual activity they hope for", "Pursuing children or assuaging partner's desire by other means" and "Difficulty making a partner continue to have sexual activity". Conclusions: Nurses should screen breast cancer patients for changes in their sexual lives and to ascertain what sexual activity means to patients, and support them in selecting appropriate coping methods.