Pain is a common problem for many older adults, with up to 50% of community-dwelling and 70% to 80% of nursing home residents experiencing pain regularly. Effective pain management requires thorough assessment, appropriate intervention, and systematic reassessment. Pain assessment, however, is complicated by dementia, which impairs memory, reasoning, recognition, and communication, and affects elders' ability to verbally report pain. As such, observational measures are needed to assess pain in this vulnerable population. The Non-communicative Patient's Pain Assessment Instrument (NOPPAIN) was developed for this purpose, but more validation of this measure is needed. Thus, the purpose of this study was to (1) evaluate reliability of the NOPPAIN tool when used by nurses and to (2) compare NOPPAIN ratings with self-report and other well-established behavioral rating procedures. Forty participants (20 cognitively intact and 20 impaired) were randomly selected for this study from a larger sample. In the parent study, participants were asked to perform everyday activities (i.e., sit, stand, walk in place, transfer in and out of bed) while being videotaped. The tapes, all previously scored using microanalytic observational coding, were rated again by naïve raters using the NOPPAIN measure. Results indicated (1) high inter- and intrarater reliability of the NOPPAIN and (2) significant correlations of the NOPPAIN with self-reported pain and detailed behavioral coding. Findings support the reliability and validity of the NOPPAIN measurement tool and suggest this easy-to-use tool may be adequate for measuring pain indicators in older adults.