Recent evidence suggests that what sustains a tumor's survival and proliferation can also subvert the immune system from its defense role. As a point of convergence for numerous oncogenic signaling pathways, Stat3 is constitutively activated in diverse human cancer cells. Activated Stat3 not only upregulates genes crucial for survival, proliferation, angiogenesis, and metastasis but also promotes expression of immune suppressive factors while inhibiting Th1 immunostimulatory molecules. By virtue of its ability to promote expression of many factors that activate Stat3 in diverse cells, Stat3 allows malignant and immune cells resonate, forming close partnership for tumor immune evasion, tumor progression, and resistance to therapies.