Homeostasis and the idea of psychological balance have existed for nearly a century (e.g., Cannon, 1932, Solomon, 1934; Tolman, 1926). Similarly, the concept has been assumed in many theories across sub-disciplines and conceptualized in various ways. Eight studies use theory and rigorous methods to validate a measure of psychological disequilibrium. Studies 1-3 develop the 5-item Psychological Disequilibrium (PDQ) scale, focusing on internal consistency and content validity. Studies 2-4 examined convergent and discriminant validity to show that PDQ is the underlying core of various constructs, while remaining uniquely distinct. Prior literature informs the test of nomological validity in Studies 5 and 6 by showing the relationship between PDQ and both negative life events and the onset of depression. Finally, goal disruption theory, is used in Studies 7 and 8 to demonstrate the predictive validity of PDQ and assess its relationship to motivational outcomes. Cumulatively, the set of studies develops the scale of psychological disequilibrium, applies the scale to a range of theories, and demonstrates the utility of the scale to broad psychological scholarship.