Shadowing is a data collection method that involves following a person, as they carry out those everyday activities relevant to a research study. This article explores the use of shadowing in a formative evaluation of a professional development school (PDS). Specifically, this article discusses how shadowing was used to understand the role of a professor-in-residence (PIR) working with a PDS, and how this role facilitates capacity building at the school. After describing what shadowing is, its uses, and challenges, a brief overview of the PDS model and the role of a PIR, the authors describe their experiences with (1) developing and managing a relationship with the PIR and (2) how validity was established for the study. The article concludes with suggestions for integrating shadowing in formative evaluations.