The growing movement toward more accountable care delivery and the increasing number of people with chronic illnesses underscores the need for primary care practices to engage patients in their own care.For adult primary care practices seeing patients with diabetes and/or cardiovascular disease, we examined the relationship between selected practice characteristics, patient engagement, and patient-reported outcomes of care.Cross-sectional multilevel observational study of 16 randomly selected practices in two large accountable care organizations (ACOs).Patients with diabetes and/or cardiovascular disease (CVD) who met study eligibility criteria (n = 4368) and received care in 2014 were randomly selected to complete a patient activation and PRO survey (51% response rate; n = 2176). Primary care team members of the 16 practices completed surveys that assessed practice culture, relational coordination, and teamwork (86% response rate; n = 411).Patient-reported outcomes included depression (PHQ-4), physical functioning (PROMIS SF12a), and social functioning (PROMIS SF8a), the Patient Assessment of Chronic Illness Care instrument (PACIC-11), and the Patient Activation Measure instrument (PAM-13). Patient-level covariates included patient age, gender, education, insurance coverage, limited English language proficiency, blood pressure, HbA1c, LDL-cholesterol, and disease comorbidity burden. For each of the 16 practices, patient-centered culture and the degree of relational coordination among team members were measured using a clinician and staff survey. The implementation of shared decision-making activities in each practice was assessed using an operational leader survey.Having a patient-centered culture was positively associated with fewer depression symptoms (odds ratio [OR] = 1.51; confidence interval [CI] 1.04, 2.19) and better physical function scores (OR = 1.85; CI 1.25, 2.73). Patient activation was positively associated with fewer depression symptoms (OR = 2.26; CI 1.79, 2.86), better physical health (OR = 2.56; CI 2.00, 3.27), and better social health functioning (OR = 4.12; CI 3.21, 5.29). Patient activation (PAM-13) mediated the positive association between patients' experience of chronic illness care and each of the three patient-reported outcome measures-fewer depression symptoms, better physical health, and better social health. Relational coordination and shared decision-making activities reported by practices were not significantly associated with higher patient-reported outcome scores.Diabetic and CVD patients who received care from ACO-affiliated practices with more developed patient-centered cultures reported lower PHQ-4 depression symptom scores and better physical functioning. Diabetic and CVD patients who were more highly activated to participate in their care reported lower PHQ-4 scores and better physical and social outcomes of care.