AbstractEpistemic trust (ET) refers to the predisposition to trust information as authentic, trustworthy and relevant to the self. Epistemic distrust – resulting from early adversity – may interfere with openness to social learning within the therapeutic encounter, reducing the ability to benefit from treatment. The self‐report Questionnaire Epistemic Trust (QET) is a newly developed instrument that aims to assess ET. This study presents the first results on the psychometric properties of the QET in both a community and a clinical sample. Our findings indicate that the QET is composed of four meaningful subscales with good to excellent internal consistency. The QET shows relevant associations with related constructs like personality functioning, symptom distress and quality of life. QET scores clearly distinguish between a clinical and community sample and are associated with the quality of the therapeutic alliance. The QET provides a promising, brief and user‐friendly instrument that could be used for a range of clinical and research purposes. Future studies with larger samples are needed to strengthen construct validity and to investigate the value of the QET to predict differential treatment responses or to study mechanisms of change.