Emotion regulation problems underlie the abnormal levels of negative or positive emotion that characterise many forms of psychopathology. Several self-report measures of emotion regulation ability exist, but many are inconsistent with contemporary emotion regulation theory, and none comprehensively assess this construct across both negative and positive emotions. In this paper, we report our attempt to remedy these measurement limitations by developing and validating the Perth Emotion Regulation Competency Inventory (PERCI), a 32 item self-report questionnaire that measures emotion regulation ability as it is defined by the extended process model of emotion regulation. In Study 1, our confirmatory factor analyses in a sample of adults (N = 231) suggested that the PERCI had a factor structure consistent with its theoretical basis and could separately measure people's ability to regulate their negative and positive emotions. All subscale and composite scores had high internal consistency reliability. Study 2 (N = 1175) replicated these findings with respect to factor structure and internal consistency reliability, and correlational or regression analyses with measures of psychopathology, emotion regulation processes, alexithymia, and interpersonal attachment style also supported the validity of the PERCI. We conclude that the PERCI appears to have strong psychometric properties. Clinical and research implications are discussed.