Background: Patient involvement has become an important and lively field of research, yet existing findings are fragmented and often contested. Without a synthesis of the research field, these findings are of limited use to scholars, healthcare providers, or policy-makers. Objective: Examine the body of knowledge on patient involvement to determine what is known, contested, and unknown about benefits, risks, and effective implementation strategies. Patient Involvement: Patients were not involved. Methods: Systematic literature review of 99 journal articles using a conceptual model integrating three levels: health systems, health providers, and patients. We extracted individual research findings and organized them into the structure of our model to provide a holistic picture of patient involvement. Results: The review highlights overlaps and conflicts between various patient involvement approaches. Our results show benefits for individual patients and the health system as a whole. At the provider level, however, we identified clear barriers to patient involvement. Discussion: Patient involvement requires collaboration among health systems, healthcare providers, and patients. We showed that increasing patient responsibility and health literacy requires policy-maker interventions. This includes incentives for patient education by providers, adapting medical education curricula, and building a database of reliable health information and decision support for patients. Furthermore, policies supporting a common infrastructure for digital health data and managed patient data exchange will foster provider collaboration. Practical Value: Our review shows how an approach integrating health systems, healthcare providers, and patients can make patient involvement more effective than isolated interventions. Such systematic patient involvement is likely to improve population health literacy and healthcare quality.