Dengue virus infection can cause mild dengue fever (DF) or severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Cytokines are believed to be involved in the pathogenesis of dengue infection. However, the role of the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) in dengue infection is unclear. In this study, serum levels of MIF in adult dengue patients with different disease severity and clinical outcome were determined and compared with the levels of other cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), IL-10, and interferon gamma (IFN-gamma), in the same patients. Serum levels of MIF, IL-6, and IL-10, but not IFN-gamma or TNF-alpha, were higher in all DHF patients who died than in DHF survivors and DF patients. We conclude that in addition to IL-6 and IL-10, elevated levels of serum MIF are a potential predictor of disease severity and clinical outcome in dengue patients.