The aim of this research is to examine the seasonal effects of exogenous melatonin supplementation on the immune system and hemato-biochemical parameters of Muzaffarnagari sheep. This study set out to determine whether melatonin may improve physiological indicators that are vital to sheep's health. The research was place at the study was conducted in Department of Veterinary Physiology and Biochemistry, College of Veterinary Science and Animal Husbandary Acharya Narendra Deva University of Agriculture and Technology Uttar Pradesh. After melatonin was given, there were noticeable changes in hemoglobin levels, leukocyte profiles, and red blood cell count, according to hematological research. Seasonal fluctuations were associated with changes in total protein levels and immunoglobulin concentrations, suggesting that melatonin may play a role in regulating immunological function. Melatonin supplementation may have therapeutic applications in livestock management, and the results highlight the impact of seasons on sheep physiology. The results of this study add to our understanding of how melatonin improves sheep health in a variety of settings by shedding light on how it affects hemato-biochemical and immunological responses.