The aim of this study is to investigate sleep quality in patients with ankylosing spondylitis (AS) and to evaluate the relationship of the disease parameters with sleep disturbance. Eighty AS patients (60 males and 20 females) fulfilling the modified New York criteria, and 52 age- and gender-matched controls (33 males and 19 females) were enrolled in the study. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Pain was measured by visual analogue scale. The disease activity and functional status were assessed by the Bath AS disease Activity Index and the Bath AS Functional Index. The Bath AS Metrology Index was used to evaluate mobility restrictions, and the Bath AS Radiology Index was employed to evaluate the radiological damage. The psychological status and quality of life were assessed with the hospital anxiety-depression scale and AS quality of life scale. The patients with AS had significantly more unfavourable scores in the subjective sleep quality, habitual sleep efficiency domains (p < 0.001) and the total PSQI score (p < 0.05). Poor sleep quality (total PSQI score) was positively correlated with increased pain, poor quality of life, higher depressed mood, higher disease activity and mobility restrictions. Pain was also an independent contributor to poorer sleep quality (p = 0.002). The sleep quality is disturbed in patients with AS. The lower quality of sleep is greatly associated with the pain, disease activity, depression, quality of life and increased limitation of mobility.