Applying qualitative and quantitative analyses across four studies and seven samples, we clarified the meaning and developed a new measure of career insecurity. Career insecurity is defined as "an individual's thoughts and worries that central content aspects of one's future career might possibly develop in an undesired manner." The new Multidimensional Career Insecurity Scale (MU-CI-S) measures eight career insecurity (CI) dimensions: (1) CI-Career opportunities; (2) CI-Decreased prestige and qualification requirements of the employment; (3) CI-Contractual employment conditions; (4) CI-Unemployment; (5) CI-Change of workplace; (6) CI-Retirement; (7) CI-Work-nonwork interactions; and (8) CI-Discrepancy between individual resources and work demands. Across all studies, the MU-CI-S showed excellent psychometric properties (e.g., factor loadings of all items and internal consistencies of all dimensions) and high levels of construct validity (e.g., theoretically assumed factorial structure and discriminant and convergent validity).The analyses showed concurrent, predictive, and incremental validity beyond neuroticism and other job and career insecurity measures for predicting health and well-being,This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.