Nitric oxide (NO) is a free radical synthesized from L-arginine by three different NO-synthases (NOS). NO exhibits multiple and complex biological functions and many of its effects can be mostly attributed to its strong oxidant capacity, which provides it a high affinity to metals, mainly metal with low spin configuration. Molecular targets of NO are diverse and include both low molecular weight species (e.g. thiols) and macromolecules that can be either activated or inhibited as a consequence of reacting with NO. Thus, NO is an important mediator of immune homeostasis and host defence, and changes in its generation or actions can contribute to pathologic states. The knowledge of novel effects of NO has been not only an important addition to our understanding of immunology but also a foundation for the development of new approaches for the management and treatment of various diseases, including Chagas’ disease. Herein, the multiple mechanisms by which NO can directly or indirectly affect the generation of an immune response against T. cruzi infection are discussed.