The quality of empathy research, and clinical assessment, hinges on the validity and proper interpretation of the measures used to assess the construct. This study investigates, in an online sample of 401 adult community participants, the construct validity of the Affective and Cognitive Measure of Empathy (ACME) relative to that of the Interpersonal Reactivity Index (IRI), the most widely used multidimensional empathy research measure. We investigated the factor structures of both measures, as well as their measurement precision across varying trait levels. We also examined them both in relation to convergent and discriminant criteria, including broadband personality dimensions, general emotionality, personality disorder features, and interpersonal malignancy. Our findings suggest that the ACME possesses incremental validity beyond the IRI for most constructs related to interpersonal malignancy. Our results further indicate that the IRI Personal Distress scale is severely deficient in construct validity, raising serious concerns regarding past findings that have included it when computing total empathy scores. Finally, our results indicate that both questionnaires display poor measurement precision at high trait levels, emphasizing the need for future researchers to develop indices that can reliably measure high levels of empathy.