Background This study aimed to investigate whether personality traits and their facets are associated with a multi-methods assessment of physical activity and walking performance and whether they explain the discrepancy between self-reported and accelerometer-assessed physical activity.

Methods The participants were community-dwelling, 70–85-year-old men and women from Finland (n = 239) who were part of a clinical trial. Personality traits and their facets were measured using the 240-item NEO Personality Inventory-3. Physical activity was assessed using questions about frequency, intensity and duration of exercise (self-reported metabolic equivalent minutes (MET)) and by tri-axial accelerometers (light and moderate-to-vigorous physical activity and total MET-minutes). Walking performance was measured by 6-min walking distance and 10-m walking speed. Linear regression analyses were controlled for age, sex, education, body mass index, disease burden, and intervention group.

Results The activity facet of extraversion was positively associated with self-reported MET-minutes, accelerometer-assessed light physical activity and walking performance. The positive emotions facet of extraversion was positively associated with self-reported MET-minutes and walking performance. Openness and its facets and the excitement seeking facet of extraversion were positively associated with walking performance. Conscientiousness and most of its facets were associated with both physical activity and walking performance, but these associations were not statistically significant after accounting for all control variables. The impulsiveness facet of neuroticism was negatively associated with accelerometer-assessed light physical activity and walking performance, but the associations with walking performance attenuated after accounting for all control variables. Accelerometer-assessed moderate-to-vigorous physical activity was not associated with personality traits or facets. Discrepancy analyses suggest that openness and the excitement-seeking facet of extraversion were associated with higher self-reported than accelerometer-assessed physical activity.

Conclusions Consistently across methods, older adults who scored higher on facets of extraversion and conscientiousness tended to be more active and outperformed peers on walking performance. Older adults who scored higher in the facets of openness and the excitement-seeking facet of extraversion had better walking performance but also overestimated their self-reported physical activity compared to the accelerometers.