Background: Surgically treatable conditions are well documented in high-income countries. There is a gap in epidemiological understanding of breast pathology in many developing countries, Timor-Leste among them. This study was conducted to determine the burden of breast disease and to inform public health measures to address early detection, diagnosis and management. Methods: A retrospective quantitative case-control study was conducted at Guido Valadares National Hospital in Dili. Patients were included if they attended surgical outpatients or had a pathology specimen recorded between 1 September 2016 and 1 September 2017. Results: There were 444 female patients with a clinical diagnosis of breast disease over the 12-month period. The average age was 33.7 years. There were 188 (42.3% of total sample) cases of fibroadenoma and 122 (27.4% of total sample) diagnoses consistent with nonspecific lumps. Of the 116 female patients presenting to Guido Valadares National Hospital who had a biopsy, 62.6% were malignant or hyperplastic in nature, and 86% of those with a malignant biopsy had clinically locally advanced disease. Conclusion: Breast conditions including cancer in Timor-Leste are relatively common and occur in young women in the prime of their lives (37 years of age). Developing a national cancer registry and funding directed towards improving early presentation and good clinical care of breast cancer patients will be critical for reducing early morbidity and mortality and improving other patient outcomes including income loss, gender health inequality and the intergenerational effects of early parental death.