OBJECTIVES: A budget impact analysis of adding erlotinib to the standard chemotherapy as first-line therapy in advanced EGFR mutation-positive non-small cell lung cancer (NSCLC) in Vietnam. METHODS: A budget impact model was developed for erlotinib-covering to the current standard chemotherapy in the healthcare plan in Vietnam over a 3-year horizon. The variation of the erlotinib introduction in the erlotinib-containing scenario was 20%, 40% and 60 % in year 1, 2 and 3, respectively. RESULTS: The covering erlotinib to the standard chemotherapy as the first-line treatment resulted in the increase in the budget of 107.8 billion VND over 3-year (211.5 billion VND and 103.7 billion, respectively). Oral erlotinib therapy notably reduced the budget related to the adverse event management and administration, 3.6 billion VND and 1.7 billion VND, respectively. However, the price of erlotinib had the most impact on the budget, raising 106.7 billion VND compared with the current strategy. CONCLUSIONS: Based on the analysis, the introduction of erlotinib monotherapy had a relatively strong impact on the healthcare budget. The price of erlotinib contributed to the impact on the budget the most.