Healthy levels of physical activity and improved fitness have shown better quality of life outcomes and improved survival in women with breast cancer. There is a lack of baseline data for fitness levels in breast cancer outpatients in Australia. A single centre cross-sectional study was performed to provide a snapshot of the fitness levels of women attending the Surgical and Oncology Breast Outpatient Clinic at Western Health, Melbourne. A total of 200 women (aged 18-85 years) were surveyed and the 6-min walk test (6MWT) was performed. Single and multiple linear regression analyses were performed. The mean 6-min walk distance (6MWD) was 486.6 m (95% CI ±12.8 m), which was comparable with reference ranges. The mean age of participants was 47.5 years. Ninety-seven (48.5%) participants had diagnosis of breast cancer. Breast cancer diagnosis had a negative effect on 6MWD of -33.6 m walked (P = 0.010). However, multiple regression analysis showed that only age (-2.6 m walked per year older; P < 0.001), body mass index (-4.2 m walked per unit of body mass index increase; P < 0.001) and presence of comorbidities (-56.9 m walked; P < 0.001) had statistically significant negative effects on 6MWD. Self-reported exercise tolerance correlated significantly with 6MWD (walking: P < 0.001 and stairs: P = 0.014). The 6MWT was easily performed within outpatient environment to accurately assess baseline level of fitness in breast cancer clinic outpatients. This indicates that 6MWT can be used as a valuable adjunctive tool to assess the level of fitness in breast cancer patients to make therapeutic recommendations in improving breast cancer outcomes.