Backround: Level one evidence reported poorer outcomes among patients taking dietary supplements after breast cancer (BC) diagnosis.Methods: We evaluated dietary supplement behaviours among adult BC patients via questionnaire. Sociodemographic data, supplement use, attitudes, and healthcare provider (HCP) advice were analysed.Results: Of 185 participants, 45% were regular supplement users following diagnosis. Regular supplement use was associated with higher education level (p = 0.05). The majority perceived supplements to be safe. Over half reported not receiving advice from HCPs.Conclusion: In summary, supplement use is prevalent among BC patients. Development of guidelines in relation to safe use of dietary supplements after cancer diagnosis is crucial.