Purpose <p>To describe upper-body function in women after breast cancer treatment; and to explore the relationship between upper-body function, quality of life and breast cancer- related lymphoedema up to 7-years post-diagnosis.</p> Methods <p>This study uses data collected in a prospective, longitudinal, population-based, breast cancer cohort study. The Disability of Arm, Shoulder and Hand questionnaire (short version -<i>Quick</i>DASH), the Functional Assessment of Cancer Therapy-Breast questionnaire (FACT-B) and self-report of a clinical diagnosis were used to assess upper-body function, quality of life and breast cancer-related lymphoedema, respectively, in 2,876 women with invasive breast cancer at three time points: baseline (up to 9&#xa0;months post-diagnosis), and at 2- and 7-years post-diagnosis. Unadjusted cross-sectional relationships between outcomes of interest were tested at each time point. Unadjusted and adjusted regression analyses were used to explore the potential predictive relationship between upper-body function and lymphoedema.</p> Results <p>Upper-body impairment was common up to 7-years post-diagnosis with &gt; 60% of women reporting at least mild impairment and 23.8–25.6% reporting moderate to very severe impairment. Impaired upper-body function at baseline assessment was associated with poorer overall quality of life (mean (standard deviation) FACT-B for no versus mild impairment: 77.5 (11.8) versus 70.9 (12.1), <i>p</i> &lt; 0.05) and increased odds of breast cancer-related lymphoedema at 2 and 7 years follow-up (moderate to severe upper-body function impairment at 2- and 7- years post-diagnosis: Odds Ratio (95% Confidence interval) 2.49 (1.57, 3.93) and 2.54 (1.51, 4.26), respectively).</p> Conclusion <p>Future research evaluating whether prospective monitoring of upper-body function and interventions that can address impairment can reduce the risk of breast cancer-related lymphoedema are warranted.</p>