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Introduction: light intensity and duration are physical factors that affect hormone secretion and circadian rhythms. This study aimed to determine the effects of various light intensities on serum melatonin and cortisol levels.  Materials and methods: This experimental study was carried out on 32 male rats: Group 1 as the control group, received a brightness of 150 lux, and groups 2, 3, and 4 as the exposure groups received light intensities of 300, 5000, and 8000 lux for 14 days, respectively. To evaluate hormone levels, blood samples were taken on before and after 7 and 14 days of exposure. Then cortisol and melatonin levels were determined by ELISA. Data were analyzed using SPSS. Results: The results showed that cortisol levels after seven days of exposure in the groups exposed to the light intensity of 300, 5000, and 8000 lux increased significantly compared to the control group, and after 14 days, the level of cortisol in the groups. Exposure to a light intensity of 5000 and 8000 lux increased significantly compared to the control. Also, melatonin levels in the group of rats exposed to the light intensity of 5000 lux and 8000 lux after 7 and 14 days of exposure compared to the control significantly decreased. Conclusion: Increased light intensity is associated  with  increased  melatonin  suppression and cortisol levels. It is suggested  that  more studies be done to prove the effect of different light intensities on changes in the levels of these  hormones at varying hours of the day.