Media and information literacy (MIL) is a key concept in several research fields and measuring the levels of MIL is considered valuable for policy stakeholders. However, the concept is complex, and few systematic reviews of research on measuring MIL levels have been conducted. This article draws on a systematic review of peer-reviewed studies measuring MIL between 2000 and 2021. Out of a total of 4008 publications, 236 were included in the analysis, and 87 were analysed in depth. A key finding was that several studies applied broad understandings of MIL, often based on initiatives by international organisations such as UNESCO, Ofcom, and EAVI. The main measuring methods in the studies were self-evaluations, knowledge claims, and demonstrated skills, all with associated possibilities and challenges. Few studies have been systematically replicated, and few have mapped larger population groups, while socio-demographic aspects have often been underestimated.