The ability of interpreters to engage in metacognitive activity enabling them to self-assess the changing purpose of their task and subsequent strategies can play a pivotal role in their global attainment levels. This paper argues that developing a high degree of metacognition can be key, not only for the expert’s interpreting performance, but also for trainees’ learning processes, helping them develop a more accurate professional self-concept and better self-regulation techniques. The study, carried out with 199 interpreting trainees, tested a tool to assess self-perceived metacognition levels. The measurement tool was developed on the basis of previous relevant academic contributions to the overlapping fields of Education, Interpreting and Psychology. According to the results of a factor analysis, self-perceived metacognition in interpreting trainees can be defined as a construct made up of four dimensions: self-knowledge perception, consolidation of one’s own set of criteria, development of a macro-strategy, and task-focused flow.