Physical activity was identified as a major determinant of longevity. Using wearable accelerometers, we evaluated energy expenditure (EE), including resting- (REE) and total-energy expenditure (TEE), physical activity level (PAL), percentage of PAL ≥ 3 metabolic equivalent tasks (METs), number of steps, resting index (RI%) and sleep patterns in 44 free-living nonagenarians (27 men) residing in a Sardinian village famous for its longevous population. The average REE and TEE recorded were 1275 ± 163 kcal/day and 2284 ± 543 in the men and 952 ± 108 kcal/day and 1810 ± 302 in the women, respectively. The average PAL was 1.8, and the percentage of physical activity >3 METs was greater than 40%. A significant negative correlation (p < 0.05) between disability and PAL was found among the women. This study provides evidence that nonagenarians from the longevous population of Sardinia show excellent physical functionality indexes. Their longevity might result, at least in part, from their ability to stay physically fit during aging.