Background: Cisplatin is considered a potent chemotherapeutic drug used in clinical oncology but causes testicular damage as a side effect. Erdosteine is a mucolytic drug possessing an antioxidant capacity. Aim of  the Work: The present study was planned to evaluate the possible protective effect of erdosteine against cisplatin-induced testicular toxicity in rats. Material and Methods: Forty adult male albino rats were divided into four groups, ten rats each: control, erdosteine-treated (50 mg/kg body weight/day, orally for 7 days), cisplatin-treated (a single dose of 7mg/ kg intraperitoneally) and erdosteine/cisplatin-treated. Erdosteine was administered 24h before cisplatin injection and was continued until animal sacrifice. Six days after cisplatin administration, all rats were anaesthetized with ether. The scrotum of each animal was incised and the testes were removed and processed to be examined by both the light and scanning electron microscopy. Results: Examination of the testicular specimens of the cisplatin-treated group revealed severe testicular damage with significant reduction in the tubular diameter and germinal epithelium thickness compared to the control group. Shrunken tubules, germ cell loss and apoptotic changes in most of the cells, especially the primary spermatocytes and round spermatids were noticed. The mature spermatids appeared markedly decreased in number and the existing ones showed abnormal forms. Increased interstitial edema and apparent decrease in the Leydig cells were also observed. Erdosteine administration before cisplatin showed amelioration of the testicular architecture. Despite the mild degenerative changes in some spermatogenic cells, cell loss was markedly decreased and most of the tubular lumina were full of mature spermatids. Apparent increase in the Leydig cells and decreased interstitial edema was also noticed. Conclusions: Erdosteine partially protected the rat testes against the cisplatin-induced toxicity most probably via its potent antioxidant and radical scavenging activities.