Background: Pain is the most common and distressing symptom for patients. 30% of adults in the United States suffer from chronic pain. The total cost of pain is much higher than the total costs of heart disease, cancer, and diabetes. The lack of health informatics tools to support acute and chronic pain management contributes to the chronic pain and opioid abuse crises. Objective: The purpose of this study was to systematically appraise the content and functionality of mobile pain management apps. Apps reviewed in this study included a pain diary feature, and we searched for apps intended for clinical usage that support (1) crossplatform compatibility, (2) clinician access to graphical pain data visualization, (3) HIPAA compliance, and (4) the validated PEG (Pain Intensity, Enjoyment of life, General activity) survey tool for primary care physicians' pain management. Methods: The Apple App Store and the Google Play Store were searched to identify pain management apps on 2/20/2018. The inclusion criteria were as follows: (1) that apps include a pain diary function allowing users to record pain episodes, (2) are available in either Apple App Store or Google Play Store, and (3) are available in the English language. We excluded apps if they were limited to only specific forms of pain or specific diseases. Results: A total of 36 apps met the inclusion criteria. Most of the apps served as pain diary tools to record the key characteristics of pain. The apps displayed many quality and usabil-