IMPORTANCE Few health systems have adopted effective dementia care management programs. The Care Ecosystem is a model for delivering care from centralized hubs across broad geographic areas to caregivers and persons with dementia (PWDs) independently of their health system affiliations. OBJECTIVE To determine whether the Care Ecosystem is effective in improving outcomes important to PWDs, their caregivers, and payers beyond those achieved with usual care. DESIGN, SETTING, AND PARTICIPANTS A single-blind, randomized clinical trial with a pragmatic design was conducted among PWDs and their caregivers. Each PWD-caregiver dyad was enrolled for 12 months between March 20, 2015, and February 28, 2017. Data were collected until March 5, 2018. Study interventions and assessments were administered over the telephone and internet by clinical and research teams in San Francisco, California, and Omaha, Nebraska. Of 2585 referred or volunteer PWD-caregiver dyads in California, Iowa, or Nebraska, 780 met eligibility criteria and were enrolled. A total of 512 PWD-caregiver dyads were randomized to receive care through the Care Ecosystem and 268 dyads to receive usual care. All eligible PWDs had a dementia diagnosis; were enrolled or eligible for enrollment in Medicare or Medicaid; and spoke English, Spanish, or Cantonese. Analyses were intention-to-treat. INTERVENTION Telephone-based collaborative dementia care was delivered by a trained care team navigator, who provided education, support and care coordination with a team of dementia specialists (advanced practice nurse, social worker, and pharmacist). MAIN OUTCOMES AND MEASURES Primary outcome measure: Quality of Life in Alzheimer's Disease based on caregiver's rating of 13 aspects of PWD's well-being (including physical health, energy level, mood, living situation, memory, relationships, and finances) on a 4-point scale (poor to excellent). Secondary outcomes: frequencies of PWDs' use of emergency department, hospitalization, and ambulance services; caregiver depression (score on 9-Item Patient Health Questionnaire; higher scores indicate more severe depression); and caregiver burden (score on 12-Item Zarit Burden Interview; higher scores indicate more severe caregiver burden). RESULTS The 780 PWDs (56.3% female; mean [SD] age, 78.1 [9.9] years) and 780 caregivers (70.9% female; mean [SD] age, 64.7 [12.0] years) lived in California (n = 452), Nebraska (n = 284), or Iowa (n = 44). Of 780 dyads, 655 were still active at 12 months, and 571 completed the 12-month survey. Compared with usual care, the Care Ecosystem improved PWD quality of life (B, 0.53; 95% CI, 0.25-1.30; P = .04), reduced emergency department visits (B, −0.14; 95% CI, −0.29 to −0.01; P = .04), and decreased caregiver depression (B, −1.14; 95% CI, −2.15 to −0.13; P = .03) and caregiver burden (B, −1.90; 95% CI, −3.89 to −0.08; P = .046). CONCLUSIONS AND RELEVANCE Effective care management for dementia can be delivered from centralized hubs to supplement usual care and mitigate the growing societal and economic b...