During the past 20 years, Situational Judgment Tests (SJTs) have developed into a viable tool in personnel selection. Despite their growing popularity, research examining the extent of measurement error is widely lacking. Using reliability generalization, the aim of this article was twofold: (1) establish an estimate for an average coefficient alpha of SJT scores across studies and (2) examine the influence of essential SJT features and selected study variables on score reliability. To handle potential dependent observations a three-level hierarchical linear model was used. The results indicate that the reliability of SJT scores is typically rather low and below recommended levels for highstakes applications. Additionally, both SJT and study characteristics affect score reliability. Implications for practitioners and researchers are provided to guide an appropriate use of SJTs and to initiate future research.