The classification of dengue virus-infected patients continues to be a challenge to researchers and clinicians in the field. The accuracy of the 1997 World Health Organization (WHO) dengue case definition has been debated for a decade, because the definition was very stringent, for instance, several researchers showed that apparently severe cases were misclassified as not severe. Therefore the WHO issued revised guidelines in 2009. Here, we retrospectively compared the performance of the WHO case definition of 2009 with the WHO case definition of 1997 in a detailed documented pediatric cohort from Indonesia. Intensive treatment intervention was used as an indicator of severity of disease. In line with our expectations, the 2009 WHO case classification proved to be significantly more specific, albeit less sensitive than the WHO case classification of 1997. We conclude that the revised classification is promising both from research and clinical perspectives, but validation of the classification criteria still needs to be addressed.