Alexithymia is a trait comprising people's ability to focus attention on and accurately appraise their own emotions. Its assessment is of clinical interest because people who have difficulty processing their negative and positive emotions are more vulnerable to developing psychopathology symptoms, however, existing alexithymia measures cannot comprehensively assess the construct across both negative and positive emotions. In this paper, we attempt to remedy these measurement limitations by developing and validating a new 24-item self-report measure, the Perth Alexithymia Questionnaire (PAQ), which is based on the attention-appraisal model of alexithymia. In Study 1, our confirmatory factor analyses in a sample of 231 adults suggested that the PAQ had a factor structure consistent with its theoretical basis; it could separately measure all components of the construct and do so across negative and positive emotions. All subscale and composite scores had high internal consistency reliability. Study 2 (N = 748) replicated these findings with respect to the PAQ's factor structure and internal consistency reliability, and statistical comparisons with measures of psychopathology and emotion regulation supported the PAQ's concurrent and discriminant validity. Our data therefore suggest that the PAQ has strong psychometric properties as a measure of alexithymia. Clinical and research applications are discussed.