There are currently more than 100 health literacy instruments. The procedures used to develop and test the measures are primarily guided by classical test theory. However, a small and growing number (n = 13) of health literacy measures are guided by modern measurement theories such as item response theory. This article briefly describes (a) the benefits of using modern measurement approaches for the development of health literacy measures, (b) how these approaches have been used with existing health literacy measures, and (c) some considerations for how modern measurement theory can help strengthen future work in health literacy measurement. Ultimately, this article provides evidence to support an assertive shift toward the use of modern measurement approaches in health literacy instrument development.