Sulfamethazine (SMZ) (1) is an antibacterial sulfa drug which suppresses the synthesis of dihydrofolic acid. It is used for the treatment of infections in livestock; such as gastrointestinal, and respiratory tract infections. During the current study, synthesis, characterization, and evaluation of immunomodulatory activities of derivatives of sulfamethazine (SMZ) (3-39) was carried out. These derivatives were synthesized by the reaction of sulfamethazine with a range of acid chlorides. All the compounds were characterized by using modern spectroscopic techniques, such as 1H-, and 13C-NMR, EI-MS, and HRFAB-MS. Compounds 3-10, 14, and 15 were identified as new compounds. Immunomodulatory effect of compounds 3-39 on different parameters of innate immune response was evaluated, including the production of Reactive Oxygen Species (ROS) from human whole blood and isolated polymorphonuclear neutrophils (PMNs), nitric oxide (NO), and pro-inflammatory cytokine TNF-α. All the new compounds, except 14 and 15, showed a significant anti-inflammatory activity. Compounds 3-39 were also evaluated for their anti-bacterial activity and cytotoxicity (3T3 mouse fibroblast cell lines). All the compounds were found to be non-cytotoxic against normal cell lines.