Background: Metabolic syndrome and the related co-morbidities can lead to impaired male reproductive function, including adverse effects on spermatogenesis and steroidogenesis as illustrated by reduced sperm number and quality, decreased testosterone levels and elevated inflammatory markers. Objective: To evaluate the impact of metabolic syndrome on androgen / estradiol ratio, semen parameters and testicular volume in adults. Patients and methods: This study was carried out on 60 adult males recruited from Al-Azhar University Hospitals outpatient clinics during the period between November 2016 and February 2021, divided into two equal groups: Group A: Males with the criteria of metabolic syndrome, and Group B: Males without the criteria of metabolic syndrome. All patients were subjected to: complete history taking, general and local examination, laboratory investigations (including total and free testosterone, serum estradiol, lipid profile, fasting blood glucose and Semen analysis) and scrotal duplex. Results: Significant decrease in both free and total testosterone in the metabolic group than the non-metabolic group. Significant inverse correlation between free testosterone / estadiol ratio and BMI, and an inverse but non statically significant correlation between free testosterone / estadiol ratio and waist circumference. Significant decrease was in both semen volume and total motility in the metabolic group than the non-metabolic group, with no statically significant difference in total sperm count, Sperm concentration, progressive motility or abnormal forms between both groups. Significant inverse correlation was found between semen volumes with BMI. Significant inverse correlation between total sperm count and sperm concentration with BMI. Significant inverse correlation was found between testicular volume on one side, and both BMI and waist circumference (WC) on the other side. Conclusion: Metabolic syndrome is directly related to a decrease in both free and total testosterone levels. Higher BMI is associated with decreased free testosterone/ estadiol ratio.