A key reason for the consistent gaps between evidence and practice across all areas of medicine is that there has been little attempt to identify or target factors critical for successful implementation of an evidence-based intervention. There is either no explicit implementation strategy or the strategy is based on a best guess rather than on a systematic assessment of crucial barriers and enablers. A different approach is needed to close the evidence–practice gap and thereby achieve the triple aim of improved health, improved patient experience and reduced healthcare costs. We present three fundamental principles of implementation science, which is a methodology that offers a systematic and comprehensive approach to improving healthcare practice and a series of ‘how to’ steps to conduct implementation science research. In an accompanying article, a scoping review of the types of implementation science research conducted in emergency medicine is reviewed, and several of the principles related to this review are discussed.