There are contradictory results in the relevant literature about the relationship between objective determinants of craniocervical posture and temporomandibular disorder (TMD), whereas no study has worked on ankylosing spondylitis (AS) and TMD relationship. We conducted this study to test the predictors of TMD in AS patients and its relationship with craniocervical posture. AS patients aged between 18 and 50 years consecutively admitted to our outpatient clinics were recruited. TMD was diagnosed by ‘Diagnostic Criteria for Temporomandibular Disorders (DC/TMD)’. Spinal mobility was assessed by BASMI; disease activity by ASDAS-CRP and neck disability by Neck Disability Index. Craniocervical posture was assessed on lateral cervical X-ray by measuring the craniocervical angle, cervical curvature angle, suboccipital distance, atlas-axis distance, and anterior translation distance. A total of 98 (58.2% female) patients with a mean age of 37.4 ± 8.2 years were enrolled in this study. TMD was diagnosed in 58 (59.2%) patients. Spinal mobility and craniocervical posture measurements were similar among the two groups. Smoking, bruxism (in females), neck disability and AS disease activity (in males) were higher in TMD patients. Multivariate analysis revealed active smoking (aOR 6.9; 95% CI 1.8-25.6; p = 0.004), bruxism in females (aOR 17.9; 95% CI 2.0-159.2; p = 0.01), high ASDAS in males (aOR 11.8; 95% CI 1.2-122.5; p = 0.038) and neck disability (aOR 12.7; 95% CI 3.8-42.9; p < 0.001) as independent risk factors for TMD in AS patients. No relationship between the craniocervical posture measurements and TMD was found in AS patients. Active smoking, high disease activity in males, bruxism in females and neck disability were found as predictors of TMD in AS patients.