The inability of nonverbal older adults to communicate pain represents a major barrier to pain assessment and treatment. This article focuses on nonverbal older adult populations with dementia, delirium, and severe critical illness. A comprehensive approach to pain assessment is advocated encompassing multiple sources of information. Selected behavioral tools for nonverbal pain assessment are critiqued. Although there are tools with promise, there is currently no standardized behavioral tool that may be recommended for broad adoption in clinical practice and continued concerted effort to this end is needed.