Tenualosa ilisha (Hamilton) is a valuable migratory fish belonging to the family Clupeidae and it is distributed in a wide area from the Persian Gulf to coasts of Pakistan and China’s southern sea. The aim of the present study was to investigate the changes occurring in innate immunity parameters during upstream migration and comparing them to those during post spawning. Sixty mature female hilsa shad were obtained using gill net from Karoon River in Khorramshahr during the spawning period (July, August and September 2014) and Hendijan coasts along the Persian Gulf coasts during post spawning period (October, November and December 2014). Immediately, blood samples were collected from the peduncle vein and then parameters including WBC (White Blood Cell) count, Differential WBC Count, plasma lysozyme content and C3 and C4 complement activity were determined. Based on the results, the levels of WBC, lysozyme and C3 during the spawning period were lower than those recorded during post spawning period. However, C₄ levels were higher during spawning (p<0.01). This fact revealed that some innate immunity parameters experience depression during upstream migration and spawning, while these parameters increase during the post spawning period, indicating the suppressive effects of spawning on fish immunity.