Brassinosteroids (BRs) are a group of phytohormones required for the regulation of growth, development and response to environmental stresses. Since their discovery in the 1970s, significant advances have been made in understanding the mechanisms of BR biosynthesis and their intricate signalling pathways and crosstalk with other plant hormones. This special issue, organized by Brigitte Poppenberger, Eugenia (Jenny) Russinova and Sigal Savaldi-Goldstein, brings together the latest research on BRs and their modes of action in a range of plants, from basic models to crops.