The rapid growth of mobile health (mHealth) led to the development of internationally harmonised guidance for software as a medical device (SaMD) by the International Medical Device Regulators Forum (IMDRF), covering definitions, risk classification, quality management, and clinical evaluation. The EU Medical Devices Regulation (MDR), applicable from May 26, 2020, onwards, specifically addresses SaMDs and adopted aspects of IMDRF guidance. In particular, Rule 11 of the MDR will have significant implications, as many products so far not classified as medical devices or as class I, may be considered class IIa, IIb, or III medical devices. The entry of technology firms into the medical device field will further drive mHealth and the incorporation of novel technologies into SaMD. This article aims to provide the relevant regulatory background information for medical writers who are requested to support the preparation of the regulatory and clinical documentation for SaMD required for MDR compliance.