Stakeholders in educational systems worldwide are increasingly recognizing the need to cater for linguistically diverse students. Adopting effective teaching practices for multilingual students has therefore become a priority in many countries (e.g. Norway: Mossige et al., 2016). With the purpose of contributing evidence-based resources, several systematic reviews have summarized past research on school-based interventions to strengthen language and literacy skills in multilingual children and adolescents. However, many of these reports have only focused on specific subgroups of multilingual students (e.g. dual language learners in the U.S. in Buysse, Peisner-Feinberg, Páez, Scheffner Hamme, 2014) and prioritized evidence coming from studies conducted in the English-speaking countries. This study aims to address these gaps by providing a systematic evidence map and overview of reviews on school-based language and literacy interventions for all types of multilingual children and adolescents. We plan to search for study reports in bibliographic databases (e.g. Eric), organizational websites (e.g. Campbell Collaboration), target peer reviewed journals (e.g. Review of Educational Research), as well as in grey literature repositories (e.g. OpenGrey). To meet inclusion criteria, reports will need to be evidence syntheses (e.g. narrative reviews) that summarize empirical research studies. Reports will need to focus on multilingual children and adolescents from 0 to 18 years of age as the population of interest. They must summarize intervention studies conducted or initiated in school settings and report outcome measures related to the participants’ language and literacy skills (e.g. vocabulary, reading skills). We will include study reports that compare the impact of interventions on language and literacy skills focusing on multilingual participants as well as reports that compare monolingual and multilingual participant groups. Information on included studies will be summarized in two phases: (1) a systematic map with descriptive data on report information, the type of review, search and inclusion criteria, and (2) a systematic overview of reviews on the identified quantitative reviews. After completing a critical appraisal based on the AMSTAR 2 tool (Shea et al., 2017), we will provide a narrative description of the available quantitative evidence (e.g. type of overall effect).