Sexuality after a cancer diagnosis has long been neglected in the clinical and research settings in many countries. In particular, research in Asia on sexuality and cancer among women is extremely scarce. Semi-structured interviews were conducted with 21 Japanese women with breast cancer (mean age 42.2 years; median length between surgery and first interview 17 months) to explore their views on sexuality following breast cancer treatment. Analysis using the Grounded Theory approach revealed four major themes: (a) hesitation in resuming sex after treatment, (b) sexual changes after resuming sex, (c) coping attitudes to the changes, and (d) long-term outcomes of the relationship with partners. Contrary to Japanese breast surgeons' optimistic outlooks, the majority of informants referred to the impact of treatment on the physical as well as psychological aspects of their sexuality. Factors that influenced women's experiences included the pace of their psychological and physical recovery after treatment, fear of their partner's negative response, the importance of the sexual relationship for the couple, and their partner's understanding and support. Suggestions for medical professionals on how to support women's sexuality after cancer are discussed with reference to the Japanese socio-cultural and medical context.