Diagnostic errors are increasingly recognized as an important—and costly—aspect of patient safety. This study advocates for engaging patients to improve diagnostic accuracy in their care and provides tactics to help patients prevent diagnostic errors, including a list of questions to ask their provider. These approaches aim to enhance clinician–patient communication and to help physicians avoid their own cognitive biases. The article also argues for the role of patients as a "crucial voice" in augmenting diagnostic delivery systems, research, and policy. A previous AHRQ WebM&M perspective with Dr. Mark Graber discussed diagnostic errors along with strategies for clinicians to avert cognitive pitfalls.