We aimed to compare self-reported adherence to the physical activity recommendation with accelerometry in older adults and to identify determinants of misperception. The sample included 138 adults age 65-75 yr old participating in the Longitudinal Aging Study Amsterdam. Participants completed a lifestyle questionnaire and wore an accelerometer for one week. More than half (56.8%) of the participants reported to adhere to the physical activity recommendation (in 5-min bouts), however, based on accelerometry, this percentage was only 24.6%. Of those who reported to adhere, 65.3% did not do so based on accelerometry. The misperceivers were older (p < .009), more often female (p = .007), had a poorer walking performance (p = .02), reported a lower social support (p = .04), and tended to have a lower self-efficacy (p = .09) compared with those who correctly perceived their adherence to the recommendation. These results suggest that misperception of adherence to the physical activity recommendation is highly prevalent among specific subgroups of older adults.