The Explicit Health Guarantees program in Chile ensures diagnosis and treatment for breast cancer (BC). However, access to palliative care, including physical, psychological, social and spiritual dimensions of patients, remains limited. This study explored barriers and facilitators to implementing access to physical therapy, nutritional counselling and mental health support services in the context of oncology care. We performed a mixed-methods design combined analysis of 2019–2023 administrative data from the Southeastern Metropolitan Health Service with qualitative interviews and focus groups involving healthcare professionals and BC patients at one public hospital and one private center. We observed a decline in referrals to supportive care from 30.2% in 2019 to 11.9% in 2023. Participants identified a lack of referral protocols, staff shortages, limited infrastructure and fragmented coordination as major barriers. Facilitators included interdisciplinary collaboration, electronic referral systems and strong patient satisfaction. Both professionals and patients valued physical therapy most highly, while private-sector patients prioritised mental health and nutritional counselling. Our findings suggest that systemic and institutional gaps translate into an underutilisation of supportive care for BC in Chile. Strengthening referral systems, expanding staff, integrating supportive services into oncology pathways and raising awareness are essential to achieve a more person-centered cancer care.