Metabolic reprogramming and immune escape play important roles in tumor development recognized as two hallmarks of cancer. The success of immune checkpoint inhibitors has opened a new era of immunotherapy for cancer treatments. Accumulating evidence suggests that metabolic adaptation of cancer cells contributes to tumor immune evasion. With high levels of metabolic activity cancer cells change metabolic pathways to meet the needs for uncontrolled growth and proliferation. The high demand for glutamine leads to many types of cancer addicted to glutamine. Altered glutamine metabolism has a significant impact on tumor invasiveness and remodeling of the tumor microenvironment. Glutamine is also a vital nutrient for the proliferation and activation of immune cells. The abundant consumption of glutamine by cancer cells can lead to immunosuppressive tumor microenvironment and resistance to immune checkpoint inhibitor therapy. In this review we provide an updated overview of glutamine metabolism of tumor cells and its involvement in tumor immune evasion and explore the potential applications of targeting glutamine metabolism to enhance anti-tumor immunity and immunotherapy.