OBJECTIVE Apathy is highly prevalent among neuropsychiatric populations and is associated with greater morbidity and worse functional outcomes. Despite this, it remains understudied and poorly understood, primarily due to lack of consensus definition and clear diagnostic criteria for apathy. Without a gold standard for defining and measuring apathy, the availability of empirically sound measures is imperative. This paper provides a psychometric review of the most commonly used apathy measures and provides recommendations for use and further research. METHODS Pertinent literature databases were searched to identify all available assessment tools for apathy in adults aged 18 and older. Evidence of the reliability and validity of the scales were examined. Alternate variations of scales (e.g., non-English versions) were also evaluated if the validating articles were written in English. RESULTS Fifteen apathy scales or subscales were examined. The most psychometrically robust measures for assessing apathy across any disease population appear to be the Apathy Evaluation Scale and the apathy subscale of the Neuropsychiatric Inventory based on the criteria set in this review. For assessment in specific populations, the Dementia Apathy Interview and Rating for patients with Alzheimer's dementia, the Positive and Negative Symptom Scale for schizophrenia populations, and the Frontal System Behavior Scale for patients with frontotemporal deficits are reliable and valid measures. CONCLUSION Clinicians and researchers have numerous apathy scales for use in broad and disease-specific neuropsychiatric populations. Our understanding of apathy would be advanced by research that helps build a consensus as to the definition and diagnosis of apathy and further refine the psychometric properties of all apathy assessment tools.