This study aims to compare physical activity (PA) level and exercise habits in patients with ankylosing spondylitis (AS) who have high disease activity with those who have low disease activity and, further, to compare both groups with population controls. Cross-sectional study design was used. The participants include 149 patients (mean age 49.3 (SD 11.1), 61% men, 54% high disease activity) and 133 controls (mean age 52.7 (SD11.3), 58% men). PA was reported with the International PA Questionnaire-Long and results were presented as weekly energy expenditure (metabolic equivalent, MET) in different intensities, domains, and proportion reaching health enhancing physical activity (HEPA). Types of PA were registered in a structured interview. The AS Disease Activity Score was used to assess patients' disease activity. Patients with high disease activity reported significantly lower total weekly energy expenditure (MET) than patients with low disease activity and controls (p = 0.02, p = 0.01, respectively) and lower amounts of walking (p < 0.01, p = 0.02, respectively) and vigorous activity (p = 0.06, p = 0.06, respectively). Only 41% of the patients with high disease activity reached HEPA compared to 61% of the patients with low disease activity (p = 0.02). Patients in general participated less in leisure PA performed outdoor and with higher intensities (MET ≥ 6) than controls.AS patients with high disease activity had lower weekly energy expenditure in PA than patients with low disease activity and controls, and were less likely to reach HEPA than patients with low disease activity. For optimal management, health professionals should focus on physical activity in their consultations with AS patients, especially those with high disease activity.