Objective: This study aimed to develop and validate a German version of the Treatment Expectations in Chronic Pain Scale (TEC) with the goal to provide a reliable instrument for the assessment of treatment expectations in chronic pain patients within the German healthcare context. Methods: A total of 153 chronic pain patients participated in the study. Participants were recruited from the outpatient and day clinics of the University Hospital Jena, which specialize in chronic pain treatment. The TEC scale was translated into German following the International Test Commission Guidelines. Psychometric evaluation was conducted using Mokken Scale Analysis, focusing on unidimensionality, scalability, and local independence. For construct validity, correlations were examined with optimism for convergent validity and with depression and anxiety for discriminant validity. Results: Unidimensionality was supported for the TEC scale overall, but local independence violations were observed for two item pairs on the Ideal Expectations subscale. Furthermore, strong ceiling effects were found in the Ideal Expectations subscale, limiting its discriminatory capacity. Scalability was higher for the Predicted subscale (H = 0.475) than for the Ideal subscale (H = 0.371). Reliability measures supported the internal consistency. No significant correlations with optimism were found for either subscale, contrary to previous findings. Discussion: The German TEC displayed a unidimensional structure and is appropriate for group-level analyses of treatment expectations. For individual comparisons, the Predicted subscale offers sufficient precision. Future studies with larger, more diverse samples should confirm these results and clarify how expectations shape adherence and outcomes. Trial Registration: German Clinical Trials Register (DRKS): DRKS00027071.