OBJECTIVES: Gastric cancer is the second most frequent cause of cancer death worldwide. Approximately 22,000 new cases are expected in Brazil annually. Our aim was to estimate the cost per disease stage of advanced gastric cancer in Brazil in the private health care sector. METHODS: A questionnaire was developed to identify the medical resource usage (MRU) of managing gastric cancer in the private healthcare system. The questionnaire was applied in a structured interview to 40 experts (20 oncologists and 20 nurses) who represented different Brazilian regions. MRU data were extracted according to the following stages: 1) diagnosis and staging; 2) 1st line treatment; 3) 2nd line treatment; 4) best supportive care (BSC), and v) terminal care. Later, a modified Delphi panel was conducted to reach a consensus on the base-case value and on possible ranges for each resource identified. A micro-costing technique was then applied to calculate costs. Financial values were translated into USD based on the exchange rate of R$2.40=US$1.0. RESULTS: The most used diagnostic procedures were upper digestive endoscopy, abdominal computed axial tomography (CAT) and thoracic radiography. 5FU/capecitabine-based chemo was the oncologists’ first choice for both 1st and 2nd line treatment (48% and 42 %, respectively).  Most commonly used resources in the BSC/ terminal care stages were medical visits and blood analysis. The mean cost per patient were: diagnostic and staging: R$1,283 (US$ 535); 1st line treatment: R$ 0.502 (US$12,710); 2nd line treatment: R$ 6,406 (US$2,670); BSC; R$6,833 (US$2,847); and terminal care: R$743 (US$310). The total mean cost per patient were R$45,768 (US$19,070), of which chemotherapy drugs represented 66%. CONCLUSIONS: The findings indicate that the most expensive stage in treating advanced gastric cancer in the private sector in Brazil is the 1st line treatment. Further studies are recommended to explore the results.