Patients, caregivers, and the public are invaluable in the evaluation and delivery of health services. This systematic review of reviews summarizes patient and public involvement (PPI) in healthcare decision-making, including outcomes that are measured and gaps requiring further research. The review identified 37 systematic reviews on PPI in healthcare decision-making; three of these focused on PPI in patient safety and the others focused on healthcare quality improvement, community-based initiatives, peer support, and healthcare professional education. Adverse events, readmissions, and mortality were commonly studied outcomes in the identified reviews of PPI in patient safety.