Immunomodulators are the molecules, drugs that have an ability to trigger the immune system either by stimulating or suppressing. It encompasses numerous stages, enzymes and regulatory mechanisms. The actual biosynthesis of immunomodulatory bioactive molecule involves combined biochemical pathway through which organisms produce compounds, that has an ability to regulate immune responses. This chapter delves into the process by which the molecules are synthesized, accentuate their biological origin and their enzymatic mechanisms that is responsible for their production. Understanding the biosynthesis pathway is crucial for illuminating the molecular structure and also the functions of immunomodulatory bioactive molecules which includes cytokinesis, chemokines, growth factors and antibodies. Understanding the biosynthesis of bioactive molecules is key step for application of biotechnology in diverse forms, which includes the optimum utilization of natural products and development of novel therapeutics which may lead to uncover the new possibilities that enhances the ability to manipulate immune responses for therapeutic responses.