Psychologists, like many health professionals, must effectively self-assess their competencies across the career trajectory in order to practice ethically and within the bounds of their knowledge and skills. Given this, research is needed to explore the cognitive process of self-assessment, and the utility of a structured measure for psychologists. This study aimed to explore: 1) how psychologists self-assess their competencies, 2) what value a structured measure has for self-assessment, and 3) the barriers or limitations to using a structured measure for self-assessment. Twelve registered psychologists were interviewed, and reflexive thematic analysis was applied. Themes were identified in the following two broad areas: 1) metacognitive processes and helpful cognitive strategies that aid self-assessment and the use of a structured self-assessment measure, and 2) barriers to self-assessment including unhelpful metacognitions about both the process of self-assessment itself, and the self. One theme and three sub-themes were identified to explain the metacognitive processes and helpful cognitive strategies described by participants, and three themes were identified pertaining to barriers to self-assessment. The current research extends the existing literature through incorporating the voice of psychologists in understanding the metacognitive processes and barriers of self-assessment, including structured self-assessment. This research has implications for health science practitioners, supervisors, educators and research.