Cadmium (Cd) is an environmental pollutant known as endocrine disruptor. Cd has been reported to induce perturbations of the testicular functions and the subsequent decline of the male fertility of both animals and humans. Chlorella vulgaris (ChV) a species of green microalga has been reported to have multiple beneficial activities such as anti-inflammatory, antioxidant, and antiapoptotic effects. Thus, this work was conducted to declare the benefits of Chlorella vulgaris (ChV) (500 mg/kg doses) against cadmium chloride CdCl2 (2 mg/kg doses) toxicity on the main and accessory reproductive organs’ weight, structure, and function of male rats. Briefly, 40 adult male rats in 4 groups (n = 10) were used as follows; control, ChV, CdCl2, and CdCl2+ChV. (i) The 1st group was kept as control fed on pellet chow and water ad libitum. (ii) The second group is Chlorella vulgaris (ChV) group fed with C. vulgaris alga for 10 days (500 mg/kg BW). (iii) The third group was administrated CdCl2 (2mg/kg BW) via subcutaneous injection (S/C) daily for 10 days. (iv)The fourth group administered both CdCl2 and ChV with the abovementioned doses daily for successive 10 days. Our observations declared that cadmium exhibited an adverse influence on the testes and prostate gland architecture indicated by seminiferous tubule destruction, testicular edema, degeneration of Leydig cells, and prostate acini damage. All together affect the epididymal semen quality and quantity including sperm viability, motility, and count. Interestingly, ChV could restore the testicular architecture and spermatozoa regeneration accompanied by semen quality improvement and increased reproductive hormones including testosterone. On the other side, ChV suppresses reactive oxygen species (ROS) formation via enhancement the antioxidant-related genes in the testicular tissue including SOD, CAT, GSH, and MDA and maintaining spermatocyte survival via suppression of apoptotic related genes including caspase3 and activating steroidogenic related genes including StAR and HSD17β3 in the cadmium-treated testes. In this study, ChV could enhance male fertility under normal or stressful conditions and ameliorate the adverse effects of hazardous heavy metals that are widely distributed in our environment. To summarize the significance of the present study, we hypothesize that Cd can disturb the antioxidant system, induce lipid peroxidation, and upregulate the apoptosis-related genes and downregulation of steroidogenic-related genes in the male genital system in addition to altering the histological architecture of testes and prostates. From these findings, we can conclude that Cd could be considered as an oxidative stress inducer at histological, physiological, and genetic levels. C. vulgaris provided protection against testicular damage caused by CdCL2 could be due to scavenging of free radicals that inhibit lipid peroxidation and enhance antioxidant enzyme activity, all together, eliminating the ROS and apoptosis in the testicular tissue and increasing the resistance against Cd-induced oxidative damage. The properties underlined the protection ability of ChV could provide scientific bases for its use as a promising natural antioxidant and therapeutic agent to ameliorate the testicular dysfunctions induced by Cd in the future