This article presents a measure of individual differences in the tendencies to worry constructively and unconstructively, called the Constructive and Unconstructive Worry Questionnaire (CUWQ). The measure is based on a control theory perspective of worry and separates the tendency to worry in a way that facilitates goal-pursuit and threat reduction (constructive worry) from the tendency to worry in a way that hinders goal-pursuit while sustaining threat awareness (unconstructive worry). CUWQ scores were validated in 2 independent nonclinical samples, including North American (Sample 1, N = 295) and Australian (Sample 2, N = 998) residents. Final factor items were selected based on Sample 1, and the measure showed good model fit through a confirmatory factor analysis in Sample 2. In addition, scores on the 2 worry factors showed criterion-related validity by statistically predicting a variety of outcomes in both samples: Constructive worry was positively associated with punctuality and wildfire preparedness and negatively associated with trait-anxiety and amount of worry. Unconstructive worry, on the other hand, was positively associated with trait-anxiety and amount of worry, and negatively associated with punctuality and wildfire preparedness. The 2 factor scores were uncorrelated in Sample 1 and positively correlated in Sample 2, thereby showing that having a tendency to worry in an unconstructive manner does not prohibit 1 from worrying in a constructive manner as well. Understanding how the 2 tendencies to worry differ from each other and separating their measurement enables a better understanding of the role of worry in both normal behavior and psychopathology.