Research on assessing or managing medication adherence applies approaches from observational, interventional, and implementation science that spans many disciplines and demands coherent conceptualization, valid methods, appropriate analyses, and complete and accurate reporting. To ensure such reporting, the European Society for Patient Adherence, COMpliance, and Persistence (ESPACOMP) Medication Adherence Reporting Guideline (EMERGE) recommends standard reporting approaches based on an accepted taxonomy. This guideline is derived from a literature review, a reactive Delphi study with 26 medication adherence experts from many countries and disciplines, and feedback from ESPACOMP members. It is designed to supplement existing guidelines for health research reporting and is structured around 4 minimum reporting criteria and 17 items reflecting best reporting practice. By enhancing and harmonizing research reporting, EMERGE aims to advance research and, ultimately, patient outcomes.