Issues addressed: This study aimed to identify risk factors associated with weight gain post a diagnosis of breast cancer in a cohort of Australian women. Methods: In this retrospective clinical audit, objectively measured weight, age and menopause status, treatment type/s, grade, stage, oestrogen receptor and progesterone receptor (PR) status were extracted for 73 breast cancer patients from an ongoing breast cancer treatment quality assurance project. Weight gain or loss was classified as a body mass increase or decrease of ≥5% of weight at diagnosis. Results: When compared to weight at diagnosis, 57% of patients maintained, 22% gained, and 21% lost weight at 24 months post-diagnosis. Factors associated with weight gain were a diagnosis of grade II (P <.001) or grade III (P <.001) compared to grade I breast cancer, and refusal of radiotherapy (P <.001). Factors associated with weight loss were being postmenopausal compared to premenopausal (P =.033), PR positive compared to PR negative (P <.001), refusal of chemotherapy (P <.001) and radiotherapy recommended (P <.001). Conclusions: The maintenance of weight in a majority of women in this cohort is a novel finding. Early identification of women at risk of weight gain post a breast cancer diagnosis can assist health professionals identify, and therefore assisting patients in the prevention and management of weight gain and associated sequela. Investigating the weight-related communications between a patient and specialist, their access to allied health professionals and social support may assist in understanding the overall positive changes in this cohort.