Worry is a phenomenon that is present in multiple psychopathologies. Given the widely accepted transdiagnostic role that worry plays in psychopathology, reliable measures for this construct are pivotal for clinical practice. The Penn State Worry Questionnaire (PSWQ) is one of the most widely used and established measures of worry in both clinical and non-clinical populations and it is accepted as a highly reliable measure. The present study aimed to examine the factor structure and psychometric properties of the PSWQ for the Portuguese population. The total sample consisted of 428 participants, 256 from the community, and 172 from the clinical population. Confirmatory factor analysis supported a model of one factor with a method factor containing the negatively worded items.