We aimed to investigate the frequency of restless legs syndrome (RLS) and the associations between RLS and quality of sleep and life in patients with ankylosing spondylitis (AS). One hundred and eight AS patients and 64 controls were included in this study. Demographics, clinical, and laboratory data were recorded. The presence of RLS was determined with face-to-face interview by an experienced neurologist based on the International RLS Study Group criteria. RLS severity was evaluated using International RLS Study Group rating scale. Sleep quality and insomnia severity were assessed by Pittsburgh sleep quality index (PSQI) and insomnia severity index (ISI), respectively. Disease-related quality of life was evaluated by AS quality of life questionnaire (ASQoL). The frequency of RLS was significantly higher in AS patients than in controls (36.4 vs. 14.0 %, p = 0.004). RLS severity score for AS patients was significantly higher than that for controls (p = 0.03). The AS patients had higher scores in the subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication domains of PSQI, and also total PSQI and ISI than controls (p < 0.05, for all). ASQoL scores were higher in AS patients with RLS compared to those without RLS (p < 0.001). RLS severity was observed to be independently associated with total PSQI, ISI and ASQoL (p < 0.05, for all). As RLS may adversely affect the sleep and quality of life in AS patients, clinicians should be aware of RLS for early diagnosis and management in AS patients.