The aim of this systematic review and meta-analysis is to closely examine the research on the beliefs of pre-service and in-service primary school teachers on multilingualism. A comprehensive review of published international literature was conducted based on an online search using Scopus, Web of Science, DOAJ, APA PsycINFO and ERIC using specific inclusion and exclusion criteria; 2100 articles were found, with 48 of these articles being included in the final corpus. A thematic analysis shows that the beliefs of the (pre-service and in-service) primary school teachers can be classified into three categories: beliefs regarding the family languages, the language of instruction and the advantages of multilingualism for children. Teachers who see multilingualism as a resource for their teaching used translanguaging, digital tools and family language support strategies. The concerns relate to material acquisition, academic regression and delayed language of instruction acquisition. The meta-analysis shows significant influence of external factors (such as participation in seminars, school atmosphere and teachers' experiences with multilingual students) on the teachers' beliefs on multilingualism.