As many performance traits, the capacity of endotherms to thermoregulate declines with age. Aging compromises both the capacity to conserve or dissipate heat and the thermogenesis, which is fueled by aerobic metabolism. Therefore, we hypothesized that selection for an increased aerobic exercise metabolism affects both the thermoregulatory traits and the age-related changes of these traits. This was tested on bank voles (Myodes glareolus) from an experimental evolution model system: lines selected for high swim-induced aerobic metabolism (A lines), which have also increased the basal and maximum cold-induced metabolic rates, and unselected (C) lines. We measured the resting metabolic rate (RMR), evaporative water loss (EWL) and body temperature in young adult and old voles at seven ambient temperatures (13 to 32°C). The RMR was 6% higher in A than C lines, but did not change with age. However, EWL was 12% higher in the old voles. An increased EWL/RMR ratio implies either a compromised efficiency of oxygen extraction in lungs or increased skin permeability. This effect was more profound in the A lines possibly due to in-line voles than in those from other groups. The thermogenic capacity (the maximum cold-induced oxygen cocreased vulnerability to aging. Only at 32°C body temperature was markedly higher in the old A-line voles than in those from other groups. The thermogenic capacity (the maximum cold-induced oxygen consumption) was decreased by about 13% in the old voles from both selection groups, but the performance of old A- and young C-line voles was similar. Thus, the selection for high aerobic exercise metabolism attenuated the adverse effects of aging on cold tolerance, but this advantage is traded off by a compromised coping with hot conditions by aged voles. Funded through NCN grant 2016/22/E/NZ8/00416 to ETS.