Background and aim: MRI (Magnetic Resonance Imaging) is one of the best diagnostic techniques in medicine. During an MRI examination, three types of field are employed to produce images. Various experimental studies have been performed about effects of each single type of field, but only few studies are available on their combination to generate MRI. The main objective of this research was to study the effects of MRI on the sex hormones and other fertility parameters in adult male rats.Methods: In this experimental study, 40 adult male Wistar rats (220±10 g) were randomly divided into two protocols. Each protocol contained two groups of exposed (10 rats) and control (10 rats) rats. Exposed groups were placed in MRI for 25 minutes. After MRI, the animals of the first protocol were placed in the holder and scrotal skin temperatures were measured by the thermometer. These animals were anaesthetized and serum samples were obtained and stored. Then, the testes were cut and weighed. After 96 hours, these experiments were repeated for the animals of second protocol.Results: Our results for the first protocol (after MRI) indicated that there were no significant effects on the testes weight, scrotal skin temperatures and serum levels of LH in the exposed rats. However, the serum level of testosterone was significantly reduced (P<0.001) and serum level of FSH was increased (P<0.001). Regarding the second protocol (96 hours after MRI), significant increase was observed for FSH, just in the exposed rats, which was similar to the first protocol (P=0.04).Conclusions: Our results suggest that MRI causes dysfunction in the secretion of some sex hormones in the adult male rats.