Individuals with inflammatory bowel disease (IBD) have been reported to be at an increased risk of infertility and sexual dysfunction. Although the relationship between them remains unclear, IBD severity is suspected to affect hormone levels and fertility. To analyze the impact of IBD severity on semen parameters and sex hormone levels in ulcerative colitis-type IBD (UC-IBD), we conducted a cross-sectional study involving 120 patients with UC-IBD in Adam Malik General Hospital, Medan, Indonesia. The patients were classified into three groups based on the Mayo score for UC, followed by a comparison of various semen and hormone parameters among these groups. In addition to the cross-sectional analysis, a simple correlation test was conducted irrespective of the patient grouping. Sperm concentration, motility, and morphology were found to decline significantly with an increase in IBD severity. Without classifying patients with IBD into subgroups, the Mayo score showed negative correlations with sperm concentration ( r = -0.375, P < 0.0001), rapid progressive motility ( r = -0.660, P < 0.0001), free testosterone ( r = -0.732, P < 0.0001), and total testosterone ( r = -0.721, P < 0.0001), and positive correlations with immotile sperm ( r = 0.660, P < 0.0001), abnormal morphology ( r = 0.657, P < 0.0001), and sex hormone-binding globulin (SHBG; r = 0.278, P = 0.002). Sperm concentration, motility, and morphology declined significantly with the severity of IBD. This study suggests a significant negative impact of IBD severity on semen quality and sex hormones.