The objective of this study was to investigate the therapeutic effect of a tumor necrosis factor-alpha (TNF-α) antagonist on the sexual quality of life of male patients with ankylosing spondylitis (AS). In this open-label study, 42 AS patients were grouped into the TNF-α antagonist treatment group and the non-TNF-α antagonist treatment group for 3 months. Clinical and laboratory indices and changes in the sexual quality of life were compared to assess the efficacy of TNF-α antagonists on sexual activity. The relationship between sexual quality and disease activity was analyzed. There were no significant differences in baseline data between the two groups. After treatment, disease activity and quality of life were improved in these two groups. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score (1.9 ± 1.6 vs. 3.0 ± 1.3, p = 0.020), erythrocyte sedimentation rate (ESR) (9 ± 7 mm/1 h vs. 18 ± 17 mm/1 h, p = 0.031), and C-reactive protein (CRP) levels (1.8 ± 2.1 mg/dl vs. 6.2 ± 8.5 mg/dl, p = 0.035) were significantly lower in the TNF-α antagonist treatment group than in the non-TNF-α antagonist treatment group. The extent of improvement in the quality of life was more evident in the TNF-α antagonist treatment group. The average degree of improvement in the quality of life was negatively related to the BASDAI score and the Bath Ankylosing Spondylitis Functional Index score in the TNF-α antagonist treatment group (r = -0.497, p = 0.018; r = -0.558, p = 0.007, respectively). Sexual quality of life and disease activity are improved after treatment with TNF-α antagonists in male patients with AS. The extent of improvement in sexual quality and disease activity are positively related.