Helminths are the most common infectious parasites of humans, causing a global burden of disease, exceeding malaria and tuberculosis in developing countries. Helminth parasites have coevolved with humans and thus are quite well adapted to survive and flourish in them. The immune response induced by the parasite is predominantly pro-inflammatory, a Th1-mediated response involving antigen-presenting cells with elevated IgE and eosinophilia. At the later stage, the parasite is capable of polarizing the Th1 response to the Th2 response, which becomes favorable for their survival for a longer period inside the host, leading to chronic infection. This chapter elaborates the intricate and complex life cycle of different helminthic parasites, the various antigenic components expressed and shed off by the parasite inside human host, the innate immune response mediate by the host against the parasite, and the survival strategies undertaken by the parasite to dampen the surveillance mechanism against them.