Objective Needs assessment is the essence of quality cancer survivorship care. The aim of this study was to explore the supportive care needs of breast cancer survivors (BCS) in the first 5 years post treatment. Methods A mixed‐methods approach was employed. A quantitative study included a Supportive Care Needs Survey, which was completed by 250 BCS to identify the level of their needs for help. The quantitative data informed semistructured qualitative interviews undertaken with 60 BCS to explore in detail their posttreatment needs and experiences. Results 32.4% and 16.8% reported 1 to 5 and greater than or equal to 6 needs for help, respectively. The regression analyses revealed that women within 2 years posttreatment and with higher educational level had higher levels of Psychological and Health Care System/Information needs. The qualitative data revealed “continuity of care” and “lifestyle advice and self‐management” as prominent survivorship concerns. It was shown that determination to continue normal life, social support, and feeling overwhelmed by information were all experienced as important influences on survivors' need for help. Conclusions Posttreatment needs vary with BCS characteristics and to the domains concerned. The approach to posttreatment care needs to be personalized and viable.