Bone metastases (BM) are still the main cause of morbidity in cancer patients because of skeletal-related events (SREs) that reduce quality of life. They have also led to increased social and healthcare costs. At present, data available on BM are insufficient. This was a multicentre prospective observational study of patients with BM from breast cancer (BC) with at least 6 months' follow-up. Information on patients at the first diagnosis of BM, including demographics and characteristics of the primary tumor and BM. Data were periodically updated by participating centres and reviewed by the coordinator centre. From October 2014 to July 2019, 618 patients with BM from solid tumors were enrolled and 220 were eligible for the present study. Median age was 62 years (range 26-86). Median follow-up was 34 months (range 6-149). At the time of enrolment, 109 (50%) had only BM (BOM) and 109 (50%) had concomitant visceral lesions and BM (BVM). Median time-to-first BM was 47 months (range 0-312) in BOM and 78.6 months in BVM patients. Disease-free interval differed on the basis of BC molecular subtype and stage. Ninety-eight BM patients had at least on SRE. Zoledronate was used in 69.1% of cases and denosumab in 28.3%. First-line treatment was hormone-based (50.7%), chemotherapy-based (38.7%) or chemotherapy- + hormone therapy-based (9.7%). Median progression-free and overall survival were 15.1 months (95% CI 12.6-18.4) and 66.8 months (95% CI 52.1-79.2), respectively. Our prospective study could substantially help to better understand the natural history of BM from BC.