Importance: Older adults with asthma have worse control and outcomes than younger adults. Interventions to address suboptimal self-management among older adults with asthma are typically not tailored to the specific needs of the patient. Objective: To test the effect of a comprehensive, patient-tailored asthma self-management support intervention for older adults on clinical and self-management outcomes. Design, Setting, and Participants: Three-arm randomized clinical trial conducted between February 2014 and December 2017 at primary care practices and personal residences in New York City. Adults 60 years and older with persistent, uncontrolled asthma were identified from electronic medical records at an academic medical center and a federally qualified health center. Of 1349 patients assessed for eligibility, 406 met eligibility criteria, consented to participate, and were randomized to 1 of 3 groups: home-based intervention, clinic-based intervention, or control (usual care). A total of 391 patients received the allocated treatment Interventions: Screening for psychosocial, physical, cognitive, and environmental barriers to asthma control and self-management with actions to address identified barriers. The intervention was delivered in the home or primary care practices by asthma care coaches. Main Outcomes and Measures: Primary outcomes were the Asthma Control Test, Mini Asthma Quality of Life Questionnaire, Medication Adherence Rating Scale, metered dose inhaler technique, and emergency department visits for asthma care. Primary analyses compared intervention (home or clinic based) with usual care. Results: Of the 391 patients who received treatment, 58 (15.1%) were men, and the mean (SD) age was 67.8 (7.4) years. After accounting for baseline scores, scores on the asthma control test were better in the intervention groups vs the control group (difference-in-differences at 3 months, 1.2; 95% CI, 0.2-2.2; P =.02; 6 months, 1.0; 95% CI, 0.0-2.1; P =.049; 12 months, 0.6; 95% CI, -0.5 to 1.8; P =.28; and overall, χ2 = 13.4, with 4 degrees of freedom; P =.01). Emergency department visits were lower at 12 months for the intervention groups vs the control group (16 [6.2%] vs 17 [12.7%]; P =.03; adjusted odds ratio, 0.8; 95% CI, 0.6-0.99; P =.03). Statistically significant improvements were observed for the intervention vs control patients in quality of life (overall effect: χ2 = 10.5, with 4 degrees of freedom; P =.01), medication adherence (overall effect: χ2 = 9.5, with 4 degrees of freedom; P =.049), and inhaler technique (metered-dose inhaler technique, correctly completed steps at 12 months, median [range]: 75% [0%-100%] vs 58% [0%-100%]). No significant differences in outcomes were observed between patients receiving the intervention in home vs practice settings. Conclusions and Relevance: An intervention directed by patients' needs and barriers improved asthma outcomes and self-management behaviors among older adults. Trial Registration: ClinicalTrials.gov identifier: NCT02316223.