PURPOSE In Tanzania, high breast cancer mortality can be attributed to delays in diagnosis and treatment initiation. We adapted the cascade analysis method to depict sequential steps along the breast cancer care pathway in a tertiary hospital in Mwanza, to identify where correction of loss to attrition would have the biggest impact on improving outcomes. METHODS This prospective cohort included adult women presenting with breast concerns between February 2020 and January 2022. Five cascade steps beginning with patients' initial clinical breast assessment (CBA) through cancer treatment were identified: (1) CBA, (2) ordering diagnostic test(s), (3) completion of diagnostic test(s), (4) receipt of final diagnosis, and (5) initiating cancer treatment. RESULTS Overall, 721 eligible women with a median age of 42.8 years (IQR, 32.5-55.0) were included. Median time from presentation to treatment initiation was 35 days (IQR, 20-63). For step 1, 39.1% (n = 282) of patients were diagnosed with a benign concern and removed from the cascade. Completion rates for steps 2-4 were 95.0%, 90.2%, and 91.0, respectively. There were 156 (45.6%) patients diagnosed with breast cancer, and for step 5, 71.2% of patients initiated cancer treatment. In steps 2, 3, 4, and 5, there was a loss of 22, 41, 34, and 45 patients, respectively. If loss was eliminated at steps 2, 3, 4, or 5, an additional 6, 12, 11, or 45 patients, respectively, would have completed the pathway. CONCLUSION Initiating cancer treatment was identified as the step with the biggest loss and, if remedied, would have the biggest impact on improving breast cancer outcomes at Bugando Medical Centre. These results will inform future programs focused on reducing overall loss in the system and supporting patients with breast cancer.