Objective.Multimorbidity, the coexistence of 2 or more conditions in an individual, is associated with morbidity and mortality in the general population. This study aims to describe the prevalence of multimorbidity in axial spondyloarthropathy (axSpA) and assess its association with disease outcome measures.Methods.This cross-sectional study was conducted within the Ankylosing Spondylitis Registry of Ireland (ASRI) cohort. Structured standardized assessment was performed. Multimorbidity was considered as the presence of at least 1 physician-diagnosed chronic condition (excluding extraarticular manifestations) in addition to axSpA. Validated outcome measures were collected: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), Health Assessment Questionnaire (HAQ), AS Quality of Life (ASQoL), and Bath AS Metrology Index (BASMI). Adjusted multiple regression was performed to investigate the association between multimorbidity and disease outcomes.Results.A total of 734 patients from 12 centers were included: 77% male, mean (SD) age 45 (12) years. Of the cohort, 55% (n = 403) were multimorbid. Multimorbid patients were significantly (p < 0.01) older than axSpA-only patients [50 (12) vs 40 (11) yrs]. Obesity was the most prevalent chronic condition, affecting 27%. Multimorbid patients had more severe disease than patients with axSpA only. After adjusting for confounders, multimorbidity was associated with higher BASDAI (ß 0.7, 95% CI 0.34–1.05), BASMI (ß 0.45, 95% CI 0.09–0.80), BASFI (ß 0.5, 95% CI 0.23–0.78), HAQ (ß 0.07, 95% CI 0.00–0.13), and ASQoL (ß 0.87, 95% CI 0.28–1.46).Conclusion.Multimorbidity is prevalent in axSpA and is associated with more severe disease.