Abstract Background: Sildenafil citrate is used for the treatment of erectile dysfunction as it maintains a long lasting erection. This drug causes nitric oxide release from the penile tissue as it acting as phosphodiestrase-5 inhibitor causing erection. Selenium plays an essential micronutrient for humans and animals acting as anti-oxidant. Aim of Study: To study the possible protective effects of selenium on the testis of the albino rats treated with sildenafil citrate by light microscopic examination and immuno-histological study. Material and Methods: Thirty adult albino rats were obtained and isolated at Faculty of Medicine, Assuit University in 2017. The animal were divided into three equal groups: group I (control group), group II; received sildenafil citrate orally in a dose of 10mg/kg body weight for 8 weeks, group III: Received selenium in a dose of 10 microgram/kg orally 8 weeks before the treatment with sildenafil citrate. Sildenafil was obtained in the form of commercially packed tablets (Viagra). Each tablet contains 100mg of sildenafil. The tablet was grinded and dissolved in 50ml saline; hence each ml of the solution contains 2mg of the drug. Each rat received 1.25ml of the prepared solution. Selenium was obtained in the form of commercially packed tablets (selenium). Each tablet contains 60 micro-grams. The tablet was grinded and dissolved in 30ml of saline, hence each ml of the solution contains 2 microgram of the drug. Each rat received 1.25ml of the prepared solution. At the end of the experiment, the testes were obtained and subjected to the light microscopic and immuno-histochemical studies using Fas-Ligand stain for detection of apoptotic cells. Results: Administration of sildenafil citrate results in loss of the normal pattern of the germinal epithelium, thickening of the connective tissue capsule and loss of some of the germinal cells. The spermatogonia appear away from the basement membrane with pyknotic nucleus and vacuolated cytoplasm. The spermatogenic cells appear with pyknotic nuclei and vacuolated cytoplasm. The interstitial tissue shows acidophilic exudates, congested blood vessels and some of the tubules appear empty. With the usage of the immuno-histochemistry, there is an increase in the number of apoptotic cells. Addition of selenium partially restored the normal contour of the tubules and normal distribution of the germinal epithelium. The thickness of the connective tissue capsule appears nearer to the normal thickness. With the usage of the immuno-histochemistry, there is a decrease in the number of apoptotic cells. Conclusion: - Sildenafil citrate has a toxic effect on all of the germinal cells. - Administration of selenium partially improves these toxic effects.