Background <p>Self-reflection, the ability to emotionally and cognitively reflect one’s experiences with the intention to gain new insights, constitutes a core competency of psychotherapists. However, research on content and quality of self-reflection is scarce and standardized instruments for respective assessments are still missing. The current study qualitatively explores <i>semantics</i> (core contents), <i>modalities</i> (qualitative differences) and <i>foci</i> (direction of reflection-focus) of self-reflection with the aim to operationalize and better understand its key characteristics.</p> Methods <p>Forty self-reflection essays, written by 10 psychology students, were analyzed by employing a combined inductive and deductive thematic analysis.</p> Results <p>In our findings, we differentiate typical <i>modalities</i>, <i>foci</i> and <i>semantics</i> of self-reflection while underlining the connections between these aspects. At the semantic level, the feeling of insecurity emerged as the most prominent impetus for self-reflection. Previous experience, patient-interaction, and external factors like time pressure, were observed to potentially influence insecurity. While assertiveness seemed to be an ineffective strategy in dealing with this feeling, tolerating it could be identified as being helpful in reducing insecurity. Additionally, we find five different modalities of self-reflection as well as inward- and outward-related reflection foci.</p> Conclusions <p>Our findings offer a first operationalization of the self-reflection competency of (prospective) psychotherapists and constitute a basis for constructing an assessment rating scale. Particularly, reflecting on dealing with insecurity has emerged as a promising key for therapeutic-skill development.</p>