Background: The subjective experience of young breast cancer (BC) women has some specifics related to the impact of illness and treatments on the issues specific to their age. The partner is most often the primary caregiver and is himself affected by the disease. A better understanding of couples facing cancer at every stage of treatment program appears crucial to improve the overall care. This study aims to better understand the quality of life of these young couples (women <45 at diagnosis), by comparing the subjective experience of patients and partners from chemotherapy (CT) to the end of treatments period. Methods: 491 couples in which the woman has non-metastatic BC (28.7% under CT, 10.2% under Trastuzumab, 33% under hormone therapy, 28.1% under supervision) completed a self-administered questionnaire assessing their subjective experience. Results: Patients report more difficulties than partners in terms of management of children and of everyday life, body image and sexuality, career management and financial difficulties. The 2 groups were comparable with regard to the feeling of couple cohesion and the deterioration of relations with relatives. In addition, patients reported more support from relatives than partners, but this support decreases along the treatment program. While overall, patients undergoing CT and Trastuzumab and their partners reported more difficulties than those under hormone therapy or under surveillance, the negative affectivity / apprehension for the futureremains stable and relatively high from CT to the end of treatment, for the patient as well as for her partner. Conclusions: The difficulties of patients appear to be particularly strong in the early course of care and decrease over time, indicating a gradual adjustment to the disease. It is the same for partners, who also have concerns. However, there are differences between the experience of patients and partners. A longitudinal follow-up assessing the couple experience in a dyadic design would allow us to support these findings, and ultimately to better assess the couples’ needs in order to better respond to it by an optimal care management, including the establishment of follow-up consultations for couples.