Background: Cadmium (Cd) is a heavy metal toxicant, present widely in our environment and workplaces.It is well known that cadmium causes adverse effects on male reproductive organs and reproductive functions in experimental animals. Objective: This experiment was designed to find out the effect of cadmium on some histological and hormonal parameters of the reproductive system of adult male rats. Methods: thirty mature albino male rat were used (Rattus rattus norvegicus albinus), as a mammalian model. these animals were divided into two groups, 15 rat / group after labeling them. The control group (G1) was orally administrated with distilled water during the 4 weeks period of the experiment and the experimental group (G2) was orally administrated with 20 ml cadmium chloride (200 mg/1L body weight) during the 4 weeks. First of all, the rat were anesthetized, after that blood aspiration using anesthetic cardiac puncture and the serum was separated and store at -20°C until assessment of FSH, LH and testosterone hormones. After that, the weight of reproductive organs (testis,epididymus and seminal vesicle) was recorded. These organs were fixed with 10% formal saline for histological study. Results: The statistical analysis shows a significant (P< 0.05) decrease in the weight of the testes and seminal vesicles when compared with control group. The results of the sperm parameters show a significant (P< 0.05) decrease in sperm concentration and a highly significant (p≤0.01) decrease in sperm motility in treated group as compared to control. The result of testicular sections in treated group shows a decrease in thickness of germ cells layer, widening of the central seminiferous tubules lumen and prominent germ cells population necrosis. Multiple vacuoles were seen within the tubules. Sertoli cells were abnormal in number and shape as compared to control. A peritubular fibrotic change had been seen also in the testicular sections. The result also shows a highly significant decrease in diameters of seminiferous tubules, primary spermatocytes, secondary spermatocytes, spermatids and increase in interstitial space when treated with cadmium compared with control group. The Levels of serum hormones shows a significant (P<0.05) decrease in the levels of testosterone and LH hormones mean in the treated group,while highly significant (ps0.01) increase in the FSH hormone mean in the treated group when compared to the levels mean of the hormone in the control group.. Conclusion: In conclusion, these findings suggest that cadmium administration with 20 ml cadmium chloride (200 mg/1L body weight) for 4 weeks during the adulthood induced damage in the reproductive organs and lead to impair the functions of sperm parameters and cause histological and hormonal alterations.