OBJECTIVES: To estimate the direct medical costs of severe acute respiratory infection (SARI) in children and adults from three Central American countries whit a bottom-up costing approach. METHODS: The costs of inpatients treatment were estimated through the retrospective bottom-up costing in a randomized sample of clinical records from SARI patients treated in teaching tertiary hospitals during 2009 - 2011 period. Activities incurred per patient were registered and a setting-specific cost per activity was acquired. Average cost per patient in the group of children and elderly adults was estimated for each country. In Nicaragua, only the pediatric population was included. Costs were expressed in local currency (2011), American dollars, and international dollars (2005) for country comparison. RESULTS: The care cost per case in children in Guatemala was the cheaper (I$971.95) compared to Nicaragua (I$1,431.96) and Honduras (I$1,761.29). In adults, the treatment cost for Guatemala was the more expensive: I$4,065.00 vs. I$2,707.91 in Honduras. CONCLUSIONS: Bottom-up costing of SARI cases allowed the mean estimates per treated case that could have external validity for the target population diagnosed in hospitals with similar epidemiological profiles and level of complexity for the study countries. This information is very relevant for the decision-making.