Background: Erectile dysfunction (ED) has considerable impact on the quality of life of middle-aged men and is a significant global health problem with estimates of 33–52% prevalence. Although the origins of ED were thought to be psychogenic or neuropathic, evidence now clearly suggests that the predominant etiology is vasculogenic. Objective: Evaluation the effect of the level of serum arginase II on erectile function. Patients and methods: The current study was carried out on 80 individuals attending the outpatient clinic of Andrology, Al-Azhar University Hospitals. Selected individuals were divided into 2 equal groups: ● Group I: Individuals with vasculogenic erectile dysfunction. ● Group II: Matched healthy individuals as controls.      All patients were subjected to full history taking including personal history, sexual history, past history of medical disorders or operations. Evaluation of erectile function using a bridged five-item version of the International index of erectile function-5 questionnaire (IIEF-5), penile duplex, general and genital examination, and measurement of serum arginase 2 were done. Results: There was a statistically highly significant difference between patients and controls as regard serum arginase 2 (ng/ml). There was marked increase in serum arginase 2 level and prevalence of ED with increased age.There was a significant correlation between serum arginase 2 level and diabetes mellitus with significant difference in serum arginase 2 level between different types of vasculogenic erectile dysfunction. The highest percentage was to corporovenogenic erectile dysfunction (45%), followed by arteriogenic erectile dysfunction (32.5%), and finally mixed type (22.5%). With increase in serum arginase 2, there will be decrease in IIEF-5 score and an increase in erectile dysfunction, and that higher levels of serum arginase 2 level was in patients with severe ED with IIEF-5 score (5-7). There was a statistically negative correlation and significant between serum arginase 2 level and IIEF-5 score. Conclusion: Arginase 2 played an important role of male sexual health as with increase age more endothelial dysfunction.