Introduction Portfolio use to support self-regulated learning (SRL) during clinical workplace learning is widespread, but much is still unknown regarding its effectiveness. This review aimed to gain insight in the extent to which portfolio use supports SRL and under what circumstances.

Methods A realist review was conducted in two phases. First, stakeholder interviews and a scoping search were used to formulate a program theory that explains how portfolio use could support SRL. Second, an in-depth literature search was conducted. The included papers were coded to extract context–mechanism–outcome configurations (CMOs). These were synthesized to answer the research question.

Results Sixteen papers were included (four fulfilled all qualitative rigor criteria). Two primary portfolio mechanisms were established: documenting as a moment of contemplation (learners analyze experiences while writing portfolio reports) and documentation as a reminder of past events (previous portfolio reports aid recall). These mechanisms may explain the positive relationship between portfolio use and self-assessment, reflection, and feedback. However, other SRL outcomes were only supported to a limited extent: formulation of learning objectives and plans, and monitoring. The partial support of the program theory can be explained by interference of contextual factors (e.g., system of assessment) and portfolio-related mechanisms (e.g., mentoring).

Discussion Portfolio research is falling short both theoretically—in defining and conceptualizing SRL—and methodologically. Nevertheless, this review indicates that portfolio use has potential to support SRL. However, the working mechanisms of portfolio use are easily disrupted. These disruptions seem to relate to tensions between different portfolio purposes, which may undermine learners’ motivation.