For the translation, transcultural adaptation and a pilot test of the instrument were done. Also, the compliance of the breast cancer patients to the treatment was measured. The questionnaire "Cancer Patient Self-Report Questionnaire Non-Adherence" was translated and adapted; and a pilot test with 30 patients was performed. For this study, the questionnaire, Morisky-Green test, was also used. A hundred and thirteen patients diagnosed with breast cancer and who used oral chemotherapy were evaluated. The evaluated patients' average age was 57 years. 82.5% of them had invasive lobular carcinoma cancer, and almost 50% had a family history of breast cancer. The evaluation of the compliance shows that only 31.85% of the patients completed the medical treatment. Patients who presented adverse reactions were more susceptible to stopping the treatment. The low compliance on the medicated treatment is worrying and shows the need to improve it and further research to identify which factors contribute to the non-compliance to such treatment.