The aim of this study was to explore the impact of ankylosing spondylitis (AS) and the disease-related variables on the patients' sexual function according to the International Index of Erectile Function (IIEF) scoring system. A total of 70 sexually active male AS patients and 60 healthy controls were enrolled in this study. Their demographic data were evaluated, and the pain was assessed according to the visual analogue scale (VAS). Laboratory tests were conducted in order to measure the C-reactive protein (CRP) and erythrocyte sedimentation rates (ESR) of the patients. The disease activity was evaluated using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). Functional statement was evaluated with the help of the Bath Ankylosing Spondylitis Functional Index (BASFI) and with the scores obtained from the spinal measurements with the Bath Ankylosing Spondylitis Metrology Index (BASMI). The Bath Ankylosing Spondylitis Radiology Index (BASRI) was used to evaluate the radiological damage. The disease-related quality of life was measured with the Ankylosing Spondylitis Quality of Life Questionnaire (ASQoL). The anxiety and depression level of the patients was revealed through the Hospital Anxiety and Depression Scale (HADS). In comparison with the healthy control group, patients with AS had significantly lower scores in each of the 5 domains of the IIEF (p < 0.0001). The BASDAI, BASFI, BASMI, BASRI, ASQoL, HADS scores and CRP levels were negatively correlated with IIEF (p < 0.05). Orgasmic function and sexual desire scores were significantly lower in patients with peripheral arthritis (p < 0.05). No significant correlation was observed with the disease duration, smoking status, pain (VAS), and ESR levels when the total scores and the scores from the domains of IIEF were compared. The multivariate regression analyses indicated that BASFI and BASMI were independently associated with the sexual function. The sexual function is impaired in male patients with AS. This impairment in the sexual function is especially correlated with the BASFI and BASMI among the clinical and laboratory parameters.