OBJECTIVES: To estimate the incremental total healthcare expenditures associated with anxiety disorders (AD) and examine the risk factors that contribute to excessive healthcare expenditures among a national representative sample of adults with arthritis in the United States. METHODS: A retrospective cross-sectional study was conducted using the 2014 Medical Expenditure Panel Survey data. Adults with self-reported arthritis who were alive and had positive healthcare expenditures were included in the study (n=7549). Total expenditures for all healthcare utilization were estimated in adults with arthritis by the presence/absence of AD. Multivariate ordinary least square (OLS) regression on log‑transformed expenditures was used to evaluate the magnitude of the association between AD and healthcare expenditures. The contribution of each construct of the Andersen’s Health Behavioral Model of Health Services Use to the difference in expenditures among adults with and without AD was evaluated using post-regression linear decomposition. RESULTS:  About 19.6 % of the US adults with arthritis also reported AD. Patients with both arthritis and AD were significantly more likely to visit the emergency department (AOR=1.30, 95%CI:1.07-1.58) compared to those without AD. The mean total expenditure was $8,516for adults with arthritis and $12,293 (SD: for those with arthritis and AD. Multivariable OLS regression analysis indicated that adults with AD had 35% (β=0.302, p<0.001) higher healthcare expenditures compared to those without AD. Post-linear decomposition analyses revealed that 41.7% to 65.5% of the differences in expenditures can be explained by the differences in the need factors of the two groups, including comorbid depression, poor health status, pain, and other chronic conditions. CONCLUSIONS: Among adults with arthritis, the excess healthcare expenditures associated with coexisting AD were mainly contributed by the needs factors. A collaborative care model which provides timely interventions for both physical and mental conditions may potentially reduce the excessive expenditures.