CONTEXT: Depression and arthritis are disabling and common health problems in late life. Depression is also a risk factor for poor health outcomes among arthritis patients. OBJECTIVE: To determine whether enhancing care for depression improves pain and functional outcomes in older adults with depression and arthritis. DESIGN, SETTING, AND PARTICIPANTS: Preplanned subgroup analyses of Improving Mood-Promoting Access to Collaborative Treatment (IMPACT), a randomized controlled trial of 1801 depressed older adults (> or =60 years), which was performed at 18 primary care clinics from 8 health care organizations in 5 states across the United States from July 1999 to August 2001. A total of 1001 (56%) reported coexisting arthritis at baseline. INTERVENTION: Antidepressant medications and/or 6 to 8 sessions of psychotherapy (Problem-Solving Treatment in Primary Care). MAIN OUTCOME MEASURES: Depression, pain intensity (scale of 0 to 10), interference with daily activities due to arthritis (scale of 0 to 10), general health status, and overall quality-of-life outcomes assessed at baseline, 3, 6, and 12 months. RESULTS: In addition to reduction in depressive symptoms, the intervention group compared with the usual care group at 12 months had lower mean (SE) scores for pain intensity (5.62 [0.16] vs 6.15 [0.16]; between-group difference, -0.53; 95% confidence interval [CI], -0.92 to -0.14; P =.009), interference with daily activities due to arthritis (4.40 [0.18] vs 4.99 [0.17]; between-group difference, -0.59; 95% CI, -1.00 to -0.19; P =.004), and interference with daily activities due to pain (2.92 [0.07] vs 3.17 [0.07]; between-group difference, -0.26; 95% CI, -0.41 to -0.10; P =.002). Overall health and quality of life were also enhanced among intervention patients relative to control patients at 12 months. CONCLUSIONS: In a large and diverse population of older adults with arthritis (mostly osteoarthritis) and comorbid depression, benefits of improved depression care extended beyond reduced depressive symptoms and included decreased pain as well as improved functional status and quality of life.