Introduction: Hospital malnutrition is a highly prevalent process with multiple causes. Early nutritional intervention improves the prognosis of affected patients and reduces health costs. Objective: To estimate the cost-effectiveness of routine care compared with early nutritional intervention, in patients at nutritional risk, in a high complexity university hospital between March and October 2012. Materials and methods: Economic evaluation study in 165 adult hospitalized medical and surgical specialty patients. The information from a quasi-experimental intervention study conducted in 2012 was taken as a reference. Patients were stratified by intervention group according to days of hospital stay, complications and nutritional status; health costs were also obtained. Results: For the early nutritional intervention group compared to routine care, the median cost per patient with complications was US$ 3,950 vs US$ 5,301; US$ 2,462 vs US$ 4,201 for hospital stay and US$ 3,627 vs US$ 5,132 for resources derived from weight optimization, respectively. Conclusion: The early nutritional intervention in patients at nutritional risk, decreased the costs derived from complications, hospital stay, and optimization of nutritional status.