Introduction Near-infrared spectroscopy (NIRS) offers valuable insights into exercise performance and enables the investigation of cerebral and muscular hemodynamic impairments associated with aging. This study aimed to examine cerebral and muscular hemodynamic adjustments during and after an aerobic exercise session in young adults and older adults. Methods Twenty young adults and 20 older adults performed moderate-intensity aerobic exercise (60%–70% of maximum heart rate) on a treadmill for 10 min, followed by 15 min of passive recovery. NIRS devices continuously monitored oxyhemoglobin (O 2 Hb) and deoxyhemoglobin (HHb) levels in the prefrontal cortex (PFC) and vastus lateralis (VL) and biceps brachii muscles (more and less active muscles, respectively). A 3-min seated baseline measurement was recorded before the exercise session. Changes in NIRS data were calculated by subtracting the values in each minute of exercise and recovery from baseline measurements. Results In young adults, but not older adults, HHb in the VL muscle increased throughout the exercise. Additionally, after the first minute of exercise, young adults exhibited a continuous rise in PFC O 2 Hb until the seventh minute, followed by stabilization; in contrast, older adults showed no significant change in PFC O 2 Hb. During recovery, young adults demonstrated a decline in PFC O 2 Hb after the second minute, persisting until the end of the recovery period. No significant adjustment was found in the muscular hemodynamics during the recovery period. Conclusion Cerebral and muscular hemodynamic changes indicate that young adults exhibit greater adjustments to exercise demands than older adults. Aging appears to impair cortical and muscular oxygenation during aerobic exercise, which may negatively affect exercise performance. These findings enhance our understanding of age-related declines in muscle and cerebral oxygen delivery and utilization, potentially contributing to reduced exercise capacity in older adults.