Health economics evidence informs health-care decision making, but the field has historically paid insufficient attention to mental health. Economic evaluations in health should define an appropriate scope for benefits and costs and how to value them. This Health Policy provides an overview of these processes and considers to what extent they capture the value of mental health. We suggest that although current practices are both transparent and justifiable, they have distinct limitations from the perspective of mental health. Most social value judgements, such as the exclusion of interindividual outcomes and intersectoral costs, diminish the value of improving mental health, and this reduction in value might be disproportionate compared with other types of health. Economic analyses might have disadvantaged interventions that improve mental health compared with physical health, but research is required to test the size of such differential effects and any subsequent effect on decision-making systems such as health technology assessment systems. Collaboration between health economics and the mental health sciences is crucial for achieving mental-physical health parity in evaluative frameworks and, ultimately, improving population mental health.