The 20-item Toronto Alexithymia Scale (TAS-20) is the most widely used instrument for assessing alexithymia, with more than 25 years of research supporting its reliability and validity. The items that compose this scale were written to operationalize the components of the construct that are based on clinical observations of patients and thought to reflect deficits in the cognitive processing of emotions. The Perth Alexithymia Questionnaire (PAQ) is a recently introduced measure and is based on a theoretical attention-appraisal model of alexithymia. An important step with any newly developed measure is to evaluate whether it demonstrates incremental validity over existing measures. In this study using a community sample (N = 759), a series of hierarchical regression analyses were conducted that included an array of measures assessing constructs closely associated with alexithymia. Overall, the TAS-20 showed strong associations with these various constructs to which the PAQ was unable to add any meaningful increase in prediction relative to the TAS-20. We conclude that until future studies with clinical samples using several different criterion variables demonstrate incremental validity of the PAQ, the TAS-20 should remain the self-report measure of choice for clinicians and researchers assessing alexithymia, albeit as part of a multi-method approach.