Cancer is multi factorial disease in which the own normal cells of body transformed to malignant cells. The cause of cancer may be chemical, biological or radiation. All etiological factors caused mutation in DNA or activation of some abnormal biological pathways. The altered genetic makeup of transformed cell give order for abnormal protein synthesis and disrupting the normal cellular homeostasis. The available therapy for cancer like Chemotherapy, Radiation and Hormonal therapy have its own limitation and toxicities. In Chemotherapy, the principle of targeting cancer cells is based on rapidly dividing property of malignant cells. But because of similar mitotic index, many time unintentionally normal cells of the body which also have same rapidly dividing property also killed and that responsible for toxicities associated with Chemotherapy. The Radiation and Hormonal therapy also linked with much toxicity due to improper targeting of normal body cells. In Immunotherapy, bodies own immune system trained in such way that it identify abnormal cancer cells based on antigen presentation on surface and killing them specifically with out harming normal cells. The available evidences also show strong correlation between dysfunction of Immune system and arising of cancer. Immunotherapy has been tried in many cancers with promising result.