Physical pain is a significant problem for many older adults, and as many as 83% of nursing home residents reportedly have pain. Unrelieved pain has consequences for elderly individuals' physical and mental health, rehabilitation, and quality of life. Evidence suggests, however, that pain is underdetected and poorly managed among older adults. This may be due, in part, to lack of congruence between patients' and caregivers' perceptions of pain. Thus, the purpose of this study was to investigate: the prevalence, location, and intensity of residents' self-rated and nursing assistants' (NA) rated pain; the congruence between residents' and NAs' ratings of pain; and resident-based and NA-based correlates of congruent and incongruent pain ratings. Participants in this study were 45 nursing home resident-NA dyads. The results indicated 49% of residents stated they experienced pain in the past week, but NAs reported that 36% of residents experienced pain during the same time interval. There was no significant association between residents' self-ratings and NAs' ratings of pain. Of the 45 paired ratings, residents and NAs were congruent in 37.7% of cases and incongruent in 62.2% of cases. Incongruent ratings included both underdetection (37.8%) and overreporting (24.4%) by the NAs. Only residents' self-rated affect (e.g., depression, well-being) was significantly associated with whether their pain was congruently assessed, underdetected, or overreported. Depression was highest in those for whom pain was not perceived by the NAs and well-being was highest in those residents who denied pain but for whom NAs reported pain. Caregiver characteristics (e.g., age, education, work experience) were not significantly associated with pain congruence outcomes. These findings illustrate the complexities of assessing pain in older adults, and the need to include nursing assistants (NAs) in educational programs focusing on managing pain in elderly nursing home residents.