OBJECTIVES: To estimate the economic cost of probable viral diarrhea in children less than 5 years old in a 130,800-chlidren cohort in Colombia.  METHODS: A descriptive study of economic costs was made. A database of 2010 attentions of a Health Insurer was analyzed. It has 1,254,000 affiliates (130,800 children under 5 years), resident in 12 Colombian departments. The cases were identified using international classification of diseases version 10 (A080, A083, A084, A085, A09X). The types, quantity and frequency of use of health services were measured. Types, quantity and frequency of use of health services were measured. The prices of services were extracted from the Colombian official prices. Median (interquartile range: IQR) of direct cost and average length of stay (LOS) in days were calculated. The costs were calculated for hospitals by levels of complexity to prices of 2011 and converted to American dollars. RESULTS: A total of 1456 cases of probable viral diarrhea were identified in children less than five years old. 184 cases (12.64%) were outpatient. Of inpatients, 42.9% were low level of complexity (LOS: 4.4), 42.8% were middle of complexity (LOS: 4.1), and 1.3% were high level of complexity (LOS: 3.4). 0.2% of patients required Intensive Care Unit (LOS: 12.6). The median of cost per outpatient case was USD$82.8 (IQR: 51-483); the median of cost per inpatient case of middle level of complexity was USD$94 (IQR: 17.4-296.6); and in high level of complexity was US$130.4 (IQR: 81.6-222.6) and in ICU US$3.341 (IQR: 1862-4821). The total cost of cases was US$182,000.3.   CONCLUSIONS: Most probably viral diarrhea cases are mild with low average of stay. Despite the introduction of the rotavirus vaccine in early 2009, probably viral diarrhea in children under 5 years in Colombia has a significant burden of disease in this cohort.