Error resulting from missed, delayed, or wrong diagnoses is estimated to occur in 10-15% of ambulatory and inpatient encounters, leading to serious harm in around half of such cases. When it comes to conceptualizing diagnostic error, most research has focused on factors pertaining to: (a) physician cognition and (b) ergonomic or systems factors related to the physician's working environment. A third factor - the role of patients in diagnostic processes - remains relatively under-investigated. Yet, as a growing number of researchers acknowledge, patients hold unique knowledge about themselves and their healthcare experience, and may be the most underutilized resource for mitigating diagnostic error. This opinion article examines recent findings from patient surveys about sharing visit notes with patients online. Drawing on these survey results, we suggest three ways in which sharing visit notes with patients might enhance diagnostic processes: (1) avoid delays and missed diagnoses by enhancing timely follow up of recommended tests, results, and referrals; (2) identify documentation errors that may undermine diagnostic accuracy; and (3) strengthen patient-clinician relationships thereby creating stronger bidirectional diagnostic partnerships. We also consider the potential pitfalls or unintended consequences of note transparency, and highlight areas in need of further research.