Introduction Certified breast cancer centers offer specific quality standards in terms of their structure, diagnostic and treatment approaches with regards to breast surgery, drug-based cancer therapy, radiotherapy, and psychosocial support. Such centers aim to improve treatment outcomes of breast cancer patients. The question investigated here was whether patients with primary breast cancer have a longer overall survival if they are treated in a certified breast cancer center compared to treatment outside these centers. Methods We used patient-specific data (demographics, diagnoses, treatments) obtained from data held by mandatory health insurance companies (gesetzliche Krankenversicherung, GKV) and clinical cancer registries (KKR) for the period 2009-2017 as well as hospital characteristics recorded in standardized quality reports. Using multivariable Cox regression analysis, we investigated differences in survival between patients treated in hospitals certified as breast cancers centers by the German Cancer Society (DKG) and patients treated in hospitals which had not been certified by the DKG. Results The sample population consisted of 143720 (GKV data) and 59780 (KKR data) patients with breast cancer, who were treated in 1010 hospitals across Germany (280 DKG-certified, 730 not DKG-certified). 63.5% (GKV data) and 66.7% (KKR data) of patients, respectively, were treated in DKG-certified breast cancer centers. Cox regression analysis for overall survival which included patient and hospital characteristics found a significantly lower mortality risk for patients treated in DKG-certified breast cancer centers (GKV data: HR = 0.77, 95% CI = 0.74-0.81; KKR data: HR = 0.88, 95% CI = 0.85-0.92). This result remained stable even after several sensitivity analyses including stratified estimates for subgroups of patients and hospitals. The effect was even more pronounced for recurrence-free survival (KKR data: HR = 0.78, 95% CI = 0.74-0.82). Conclusions Patients who are treated by an interdisciplinary team in a DKG-certified breast cancer had clear and statistically significantly better survival rates. Certification is therefore an effective means of improving the quality of care, and more patients should be treated in certified breast cancer centers.