Diagnostic errors are rapidly gaining attention as the next frontier in patient safety, driven by studies of their incidence in malpractice claims and autopsy reports. On the other hand, checklists have become popularized in health care as a tool to promote safe practices. This commentary explores the application of checklists to the diagnostic process. The authors suggest three types of checklists: a general one that prompts providers to optimize their cognitive approach, a differential diagnosis checklist to ensure correct diagnoses are considered, and a checklist of common pitfalls and cognitive forcing functions to improve evaluation of certain diseases. Specific examples of checklists are provided with a discussion of future directions to study their adoption and impact. A past AHRQ WebM&M perspective and interview discussed diagnostic errors in medicine.