Journal of Humanistic Psychology, Ahead of Print. Grounded in a tripartite existential meaninglessness model, the authors developed the 18-item Existential Meaninglessness Scale (EMS) to assess one’s concern and anxiety of existential meaninglessness. Across three samples, the EMS’s factor structure and evidence of convergent, criterion-related, and incremental validity, internal consistency, and test–retest reliability were examined. Exploratory factor analyses demonstrated three dimensions of the EMS: incomprehension, purposelessness, and insignificance. Confirmatory factor analyses revealed that a bifactor model was a better fit to the data than other models. The bifactor model provided evidence for a general factor and measurement invariance. Ancillary bifactor indices indicated EMS’s unidimensionality. Findings of bivariate correlations and hierarchical regression analyses provided evidence for different aspects of construct validity and internal consistency. Both the Concern and Anxiety measures of the EMS positively predicted depressive symptoms and suicide ideation above and beyond the effects of general existential meaninglessness, general feelings of anxiety, and presence of meaning in life. Based on the findings, the authors discuss future research directions on existential meaninglessness using the EMS.