Background: Patient Navigation Program (PNP) assists patients to reduce delays in diagnosis and treatment. A study was conducted on how PNP in Rio de Janeiro, Brazil, could promote adherence to the "Law of 60 Days", which states that all patients with cancer within the public system should start treatment within 60 days after diagnosis of cancer. Materials and Methods: From August 2017 to May 2018, 105 patients aged 33-80 years (mean 59 years) were recruited for Patient Navigator. Follow-up was by phone, email, or text message. PNP implemented at Rio Imagem was designed to: 1) collect important data on specific barriers, and 2) ensure that at least 70% of the patients recruited with breast cancer initiate treatment within the mandatory 60-days period. Results: Patients presented with stage 0 (4%), I-IIA (38%), IIB-IIIB (48%) and IV (5%). These included barriers to compliance with the law: fear and fatalistic thoughts (99%), financial burden (79%), uncoordinated health care (76%), attitudes towards providers (75%), duplicity of pre-treatment exams (52%), patient-provider communication (52%), transport (42%), scheduling (24%), and queues for surgical treatment (12%). PNP had 100% patient satisfaction and in 52% of the cases it helped the patients to start treatment within the period established by law. Conclusion: PNP in Rio did not reach the success rate a 70% to comply with the law, as intended (it reached 52%). However, the barriers that PN did not manage to overcome the lack of human resources and medical supplies, were informed to the health authorities and to the hospital managers.