Objectives: To develop the first item bank to measure stress resilience (SR) in clinical populations. Study Design and Setting: Qualitative item development resulted in an initial pool of 131 items covering a broad theoretical SR concept. These items were tested in n = 521 patients at a psychosomatic outpatient clinic. Exploratory and confirmatory factor analysis, as well as other state-of-the-art item analyses and item response theory were used for item evaluation and calibration of the final item bank. Results: Of the initial item pool of 131 items, we excluded 64 items (54 factor loading <0.5, four residual correlations >0.3, two nondiscriminative item response curves, and four differential item functioning). The final set of 67 items indicated sufficient model fit in confirmatory factor analysis and item response theory analyses. In addition, a 10-item short form with high measurement precision (SE ≤ 0.32 in a theta range between −1.8 and +1.5) was derived. Both the SR item bank and the SR short form were highly correlated with an existing static legacy tool (Connor-Davidson Resilience Scale). Conclusion: The final SR item bank and 10-item short form showed good psychometric properties. When further validated, they will be ready to be used within a framework of computer-adaptive tests for a comprehensive assessment of the stress construct.