This article offers a new view on ‘period’ or – as we propose to call it – ‘historically informed’ costume. We consider ‘historically informed’ costume a product of a specific mode of creation, but also and especially a process of research, which brings new insights both into the history of costume and performance. After a brief overview of approaches to period costume through the twentieth century, and its use in ‘historically informed performance’, we present a methodology developed through five years of collaboration between costume maker, historian and performers within the research project Performing Premodernity. This methodology employs comparative research of material, visual and textual sources, and making and performing experiments, often in historical spaces. It stresses an experimental and collaborative approach to research and creation, in which each member brings their expertise and way of doing that complement one another. Furthermore, the methodology promotes connections between objects – costumes and bodies – which inform each other through the historicity of their practice.