The assessment of workplace learning by educators at the workplace is a complex and inherently social process, as the workplace is a participatory learning environment. We therefore propose seeing assessment as a process of judgment embedded in a community of practice and to this purpose use the philosophy of inferentialism to unravel the judgment process of workplace educators by seeing it as an interrelated system of judgments, actions and reasons. Focussing on the unfolding of a process, we applied a longitudinal holistic case study design. Results show that educators are engaged in a constant judgment process during which they use multiple and adaptive frames of reference when forming their judgment about students. They construct an overarching image of students that develops throughout the placement, and their judgments about students go hand in hand with their actions relating to fostering independent practice.