“Social stories” are used in educational interventions for subjects with Neurodevelopmental Disorder (NDD) to help them gain an accurate understanding of social situations, develop autonomy and learn appropriate behavior. Traditionally, a Social Story is a short narrative that uses paper sheets, animations, or videos to describe a social situation of every day life (e.g., “going to school”, “visiting a museum”, “shopping at the supermarket”). In our research, we exploit Wearable Immersive Virtual Reality (WIVR) technology to create a novel form of social story called Wearable Immersive Social Story (WISS). The paper describes the design process, performed in collaboration with NDD experts, leading to the definition of WISS. We also describe an authoring tool that enables therapists to develop WISSes and to personalize them for the specific needs of each person with NDD.