Objective: To identify the clinical features of elderly-onset rheumatoid arthritis (EORA) and their impact on disease outcome. Methods: A total of 3169 rheumatoid arthritis (RA) patients were recruited as part of the Korean Observational Study Network for Arthritis, the nationwide cohort of South Korea. Patients were stratified according to age at disease onset: <40 years (younger age-onset RA, n = 1167), between the ages of 40 and 59 (middle-aged-onset RA, n = 1516), and ≥60 years (EORA, n = 486). To evaluate the significance of differences in clinical features among these 3 groups, we performed analysis of variance (anova) and the χ2 test. We used multivariable logistic regression analysis to examine the association of onset age with functional disability measured with Health Assessment Questionnaire-Disability Index (HAQDI). Results: EORA patients were associated with high HAQDI (≥1) in bivariable analysis [odds ratio (OR) 1.36, confidence interval (CI) 1.04-1.77]. However, in multivariable analysis, not elderly onset but patients' age, female gender, high disease activity, disease duration over 10 years, and comorbidity with cardiovascular disease were associated with high HAQDI. Only in a predefined subgroup with disease duration <10 years, elderly onset was an independent influencing factor for the functional disability of RA patients (OR 3.04, CI 1.85-5.67: disease duration of <5 years, OR 3.07, CI 1.64-5.74: disease duration of 5 to 10 years). Conclusions: Disease onset in older age was associated independently with functional disability of RA patients who have relatively short disease duration.