To evaluate whether a Breast Cancer (BC) Patient Navigation Program (PNP) contributes to increasing compliance with the "60-Day Law, " which mandates that cancer treatment must start within 60 days of a definitive diagnosis. Consequently, to assess if complying with this Brazilian federal law helps reduce BC mortality in public health system patients. Patients and Methods: We conducted a longitudinal observational and retrospective study with women over 18 years of age diagnosed with BC. Data were collected from medical records via the PNP. The sample was selected based on an exploratory evaluation of records from the Rio Imagem Diagnostic Center and Heloneida Studart State Hospital in Rio de Janeiro, from 2017 to 2022. Active case follow-up involved cross-referencing medical records and contact via phone or text messages. Results: Out of 1,022 women diagnosed with BC, 840 were eligible after excluding those lost to follow-up, who refused treatment, died of unrelated causes, or received palliative care. 79 patients died from BC. The 5-year specific survival rate was 92.6%. Survival was higher for patients treated initially with surgery (97.9%, p < 0.0001), histological grade 1 (94.5%, p = 0.002), Luminal biological profiles (98.4%, p < 0.0001), and treatment within 60 days (95.3%, p = 0.005). Stratifying 5-year mortality risk by advanced stage revealed higher mortality among women who were not treated within 60 days as per the law (HR=2. 00[1.23; 3.24]). Conclusion: Failure to comply with the "60-Day law" doubled the risk of mortality from BC. Patients starting treatment within 60 days had higher survival rates compared to those who did not. In Brazil, the PNP could be an opportunity to properly implement existing legislation, potentially significantly impacting BC control.