The present study tested the supposition that greater levels of couple identity (or we-ness) increase a woman's coping self-efficacy in relation to breast cancer, which, in turn, predicts better psychosocial adjustment. Women (N = 112) in committed relationships completed surveys assessing their levels of couple identity, cancer coping self-efficacy, and aspects of their psychosocial adjustment (specifically, depression, anxiety and functional well-being) during one of their outpatient visits to the cancer centre. As predicted, the more women identified with their relationships, the lower their levels of depression and anxiety were and the greater their functional well-being was. This relationship was mediated by coping self-efficacy: greater identification with one's relationship predicted greater confidence in one's ability to cope, which, in turn, predicted better adjustment. The role intimate relationships play in women's adjustment to breast cancer, as well as directions for further research, are discussed.