This special issue consists of five original research papers from four European countries. By applying different methodologies (qualitative, quantitative, and mixed-methods), the contributions aim to better understand teachers’ beliefs about multilingualism in a time of increasingly globalised societies and intensified migration flows. The studies cover all educational stages and include pre-service as well as in-service teachers, and teacher educators. Both individual and collective beliefs are considered. While two of the studies are cross-sectional, the other three apply a pre-post study design in order to investigate whether teachers’ beliefs can be influenced through adequate learning opportunities. The special issue is wrapped up by a commentary piece that links the findings and issues raised by the individual papers and addresses four pressing matters which should be considered to advance further research on teachers’ beliefs about multilingualism. In this editorial, we briefly introduce the concept of teachers’ beliefs and explain its relevance for teaching and learning in multilingual settings. Based on an ongoing review study, we provide a summary of the most commonly used methodologies in research on teachers’ beliefs about multilingualism. We conclude with a summary of the five original papers as well as the commentary piece in this special issue.