Enhancing patient engagement is a priority for patient safety efforts. This quality improvement study drew from the OpenNotes project, in which patients are given access to electronic clinician documentation. Patients were asked to provide feedback and note any inaccuracies, omissions, or safety concerns in a reporting tool. As with prior studies of OpenNotes, a minority of patients elected to read the documentation; of those, the majority did not provide feedback to clinicians. The study team's clinician review panel assessed patient concerns and shared reports deemed to be safety issues with the clinicians who wrote the notes. About one quarter of patient feedback reports were considered safety concerns, and more than half resulted in the clinician making a change to the health record. The authors conclude that patient feedback on clinical notes can improve documentation and enhance detection of safety hazards.