Immune evasion is one of the hallmarks of cancer and the dynamic interaction of the immune system and tumor is of great importance for understanding of cancer pathogenesis. The investigation of cancer immunology has begun from the early years of the 20th century and has been advanced in recent decades to the extent that many immune-based interventions have been applied for cancer treatment and resulted in improvement of patients’ survival. There are a lot yet to be undertaken in this field; therefore, a profound understanding of the roles of the immune system in cancer eradication and progression can assist the researchers and clinicians to design and apply more effective and safer modalities for cancer treatment or prevention.