ABSTRACT Aims To evaluate the prevalence of frailty and its impact on quality of life (QoL) in older Chinese breast cancer (BC) patients, which have not been thoroughly reported in this population. Design A prospective multi‐centre cross‐sectional registry study. Data Sources Data were collected from Cancer Hospital of the Chinese Academy of Medical Sciences, Peking University Third Hospital and Beijing Chaoyang District San Huan Cancer Hospital between October 2021 and July 2023. Methods BC patients aged over 65 years were enrolled in this study. They completed three assessment scales including the FRAIL scale, Hospital Anxiety and Depression Scale (HADS) and European Organization for Research and Treatment of Cancer Quality of Life questionnaire Core 30 (EORTC QLQ‐C30), to screen for frailty, related factors and QoL. Clinical and pathological data were also collected. Analysis of frailty and prefrailty risk factors was performed via logistic regression. A multivariable linear regression model was used to evaluate the mean differences in scores for each QoL domain between patients with different frailty statuses. Results A total of 946 patients were enrolled from three hospitals in Beijing between October 2021 and July 2023. Their median age was 69 years and 73.6% of them had early‐stage breast cancer. Further, 37.2% of these patients had ≥ 1 comorbidity. The prevalence of frailty was 8.8% and frailty was more common in those with aged ≥ 75 years (22.3%), those with advanced tumours (15.6%), those with anxiety (31.3%) and those with depression (29.3%). More than half (57.2%) of the patients were prefrail. Regression analysis revealed that older age (odds ratio [OR] 1.12 [95% CI 1.07–1.17], p < 0.001), an advanced tumour (OR 2.27 [1.33–3.89], p = 0.003), anxiety (OR 2.74 [1.37–5.48], p = 0.004) and depression (OR 3.84 [1.97–7.49], p < 0.001) were significantly associated with frailty. After adjusting for other factors, different frailty states were shown to be independent influencing factors for QoL in both the functional and the symptom domains (all p < 0.05). Conclusions Our study provides data on the prevalence of frailty and prefrailty in older Chinese patients with BC. Both conditions are closely related to poor QoL. It is helpful for oncologist and clinical care to making intervention and better treatment decisions. Reporting Method The study adhered to the STROBE checklist. Implications for the Profession and Patient Care This study provides detailed data on the prevalence of frailty in older Chinese patients with BC and correlative factors. It suggests that clinical care should fully assess patients' frailty before making treatment decisions and provide early intervention for related factors. Patient or Public Contribution Patients participated in the implementation of the project (including the informed consent and questionnaire process). No other public contribution to this research. Relevance to Clinical Practice This study provides data on the prevalence of frailty in Chinese older BC patients and correlative factors. It indicates that clinicians should fully assess patients' frailty before making treatment decisions and provide early intervention for related factors. Trial Registration ChiCTR2200056070