Like all human senses, the sense of olfaction (smell) plays an important role in person's life. The sense of smell serves as a first warning signal, warning to the smoke of a fire, spoiled food, or the odor of a natural gas leak or dangerous fumes. Olfactory mucosa is a component of nervous system which regenerate throughout person's lifetime. Dysfunction of olfactory sensitivity may be a side effect of chronic use of high sildenafil doses. Sildenafil is oral drug effective for erectile dysfunction in men, and approximately 20% of patients complain about nasal congestion after sildenafil administration. Aim of this study was to evaluate effect of long-term sildenafil administration on rat olfactory mucosa. Forty-five male albino rats were divided into three equal groups, group I kept as control. Rats in groups II and III received sildenafil citrate orally at doses of 50 mg/kg and 100 mg/kg, respectively for three months. At the end, olfactory mucosa removed, fixed in proper fixations for histopathology, immunohistochemistry, and SEM. Results revealed that rats treated with high dose of sildenafil revealed loss of smell as well as alteration of histological pictures, immunohistochemical staining of apoptotic markers and SEM of olfactory mucosa while the rats in group II revealed normal sense of olfaction and normal histology of olfactory mucosa. In conclusion, chronic use of 100 mg sildenafil citrate led to olfactory dysfunction through stimulation of iNOS and Caspase 3 apoptotic markers whereas low dose needs further investigation and may introduce a prospective therapy for a post COVID 19 dysfunction.