OBJECTIVE The aim of this study was to assess the protective effect of the melatonin-caffeine combination against γ radiation-induced alterations in the morphological characteristics of sperms. METHODS C57BL/6 male mice (n = 30) were randomly divided into five groups: control, radiation (2 Gy), melatonin (100 mg/kg body wt.) + radiation (2 Gy), caffeine (30 mg/kg body wt.) + radiation (2 Gy), melatonin-caffeine (100-30 mg/kg body wt.) + radiation (2 Gy). METHODS All the mice were sacrificed 24 h postirradiation, and cauda epididymis was collected. In this study, sperm concentration along with any abnormality in their morphology (amorphous heads, pinheads, hookless, coiled tails, midpiece defect, and tail-less) was observed in the control and treatment group of animals. RESULTS Radiation exposure (2 Gy) considerably decreases the sperm count when compared with the control group. However, pretreatment with melatonin and melatonin-caffeine combination before gamma irradiation increased the sperm count (P < 0.05), but with caffeine alone could not produce a significant difference. The higher rate of abnormal sperms was observed in the γ-irradiated mice when compared with the control group (P < 0.05). Besides, the numbers of sperm that are hookless and coiled tails were significantly increased after irradiation. Melatonin significantly reduced the number of sperm with amorphous heads and coiled tails. Melatonin-caffeine combination further reduced sperm malformations when compared with the melatonin + 2 Gy radiation and caffeine + 2 Gy radiation group. CONCLUSIONS This study suggests that caffeine exerts a protective effect when given in combination with melatonin against gamma irradiation in sperms of C57BL/6 mice and could be a potent combination for the development of radioprotector.