OBJECTIVE: To determine the incremental cost-effectiveness and net benefit of a depression collaborative care program compared with usual care for patients with diabetes and depression. RESEARCH DESIGN AND METHODS: This article describes a preplanned subgroup analysis of patients with diabetes from the Improving Mood-Promoting Access to Collaborative (IMPACT) randomized controlled trial. The setting for the study included 18 primary care clinics from eight health care organizations in five states. A total of 418 of 1,801 patients randomized to the IMPACT intervention (n = 204) versus usual care (n = 214) had coexisting diabetes. A depression care manager offered education, behavioral activation, and a choice of problem-solving treatment or support of antidepressant management by the primary care physician. The main outcomes were incremental cost-effectiveness and net benefit of the program compared with usual care. RESULTS: Relative to usual care, intervention patients experienced 115 (95% CI 72-159) more depression-free days over 24 months. Total outpatient costs were 25 dollars (95% CI -1,638 to 1,689) higher during this same period. The incremental cost per depression-free day was 25 cents (-14 dollars to 15 dollars) and the incremental cost per quality-adjusted life year ranged from 198 dollars (144-316) to 397 dollars (287-641). An incremental net benefit of 1,129 dollars (692-1,572) was found. CONCLUSIONS: The IMPACT intervention is a high-value investment for older adults with diabetes; it is associated with high clinical benefits at no greater cost than usual care.