ObjectiveWe determined whether socioeconomic status (SES) and sex are associated with functional status (FS) in axial spondyloarthritis (axSpA).MethodsWe conducted a cohort study of patients with axSpA in the Rheumatology Informatics System for Effectiveness (RISE) registry. We performed cross‐sectional and longitudinal analyses of FS through the Multi‐Dimensional Health Assessment Questionnaire (MDHAQ) using GEE models. Area Deprivation Index (ADI) was used as an SES proxy. The cross‐sectional analysis tested for a linear trend across ADI quintiles for MDHAQ. The longitudinal analysis’ outcome was functional decline. We reported predictive margins and assessed for interaction with sex. In the longitudinal analysis, we reported odds of functional decline.ResultsIn the cross‐sectional analysis (N=5,658) mean (SD) age was 53.8 years (15.2), 55.8% were female, and 71.4% were non‐Hispanic White. Average (SD) MDHAQ was 1.6 (2.0) in men vs. 2.1 (2.2) in women. Predicted mean MDHAQ score was 2.2 (95%CI 1.8‐2.7) for the lowest ADI quintile and 1.8 (95%CI 1.4‐2.1) for the highest. Women had lower FS compared to men across quintiles. In the longitudinal analysis (N= 2,341) the proportion with FS decline was 14.3% (95% CI 7.6%‐25.5%) for the lowest SES quintile compared to 9.6% (95% CI 5.2%‐17.1%) for the highest. Women had 1.7 (95%CI 1.3‐2.2) times higher odds of functional decline compared to men. There was no interaction with sex.ConclusionsIn this large sample of axSpA patients, those with lower SES had worse FS and functional decline. Women had worse FS than men, initially and over time.