Drawing on empirical data from case study research exploring the working lives and practices of school business leaders in the English school system, this article explores the notion of professional development among this relatively under acknowledged cohort of the school workforce. I adopt the position that professional development must be understood as a multi-dimensional concept constituting both formal and informal processes. It is the latter of these two with which the article is concerned, to illuminate aspects of professional development among school business leaders in England that are often concealed within the everyday interactions and routines of working life and therefore potentially unrecognised and unappreciated as developmental. This article contributes to a burgeoning knowledge base surrounding what seems to be an under-acknowledged constituency of the school workforce, by highlighting the informal ways in which school business leaders enhance their professional development.