Abstract Background: Sildenafil citrate used for treatment of erectile dysfunction and was reported to be supportive to men with erectile dysfunction including who suffer from diabetes, hypertension, spinal cord injuries, multiple sclerosis, depres-sion, schizophrenia and men after prostatectomy. Selenium has a considerable attention as an essential micronutirent for both animal and human being. It is a potentially antioxidant agent. Aim of Study: This work aimed to study the possible protective effects of selenium on the testes of the adult albino rats treated with sildenafil citrate by transmission electron microscope. Material and Methods: Thirty adult albino rats were used and 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 10mg/kg orally before the treatment with sildenafil citrate. At the end of the experiment, the testes were obtained, and subjected to the transmission electron microscopic studies. Results: After treatment with sildenafil citrate spermato-gonia appeared with shrunken nucleus and vacuolated cyto-plasm. Sertoli cells appeared dislocated with ill-defined cell membrane. The primary spermatocytes and spermatids ap-peared with irregular shaped nuclei and abnormal acrosomal cape. Leyding cells appeared with irregular nuclei and vacu-olated cytoplasm. Spermatozoa appeared distorted with swollen mitochondrial sheath. Selenium showed some improvement in the ultrastrucure of the testis with spermatogonia appeared with large nucleus and less vacuolated cytoplasm. Sertoli cells appeared at their normal sites with indented euchromatic nucleus. Primary spermatocytes and spermatids appeared with normal shape. Leydig cells appeared with less vacuolation and euchromatic nuclei. Most of spermatozoa appeared with intact form. Conclusion: Sildenafil citrate had a toxic effect on all of the germinal cells and administration of selenium partially improved these toxic effects.