Although TNF-α possesses promising anticancer activity, clinical application is limited partly due to cardiovascular toxicities. TNF-α effects on vessels are likely related to vascular toxicity, but much remains poorly understood. Similarly, IL-2 is an attractive treatment option for cancers but its clinical use is limited by the side effect of vascular leak syndrome (VLS). We report here that TNF-α alone can trigger VLS. Administration of recombinant TNF-α induced VLS in normal mice and TNF-α transgenic mice exhibited VLS. Perivascular infiltrates in the lungs and specific cytokines in serum were observed in VLS-induced mice. This study shed a new light on the critical role of the TNF-α in IL-2-induced or non IL-2-induced VLS and provides important points to TNF-α therapy.