The objective of this study was to examine age-related effects on behavioral performance and metabolic activity of the prefrontal cortex (PFC) in a dual-task paradigm involving fine-motor control and executive-function control. Thirty-one adults (20 ± 1.1 years) and 33 older adults (70.7 ± 5.1 years) performed, separately and then concurrently, a modified Fitts task on targets of different sizes (Index of Difficulty: ID = 3; 4; 5 bits) and the random number generation task (RNG). Movement time (MT) and count score (CS) were the dependent variables for the modified Fitts task and the RNG task, respectively. Relative changes in concentrations of oxyhemoglobin [HbO2] and deoxyhemoglobin [HHb] were recorded continuously on the left and right PFCs, with near-infrared spectroscopy (Oxymon MkIII-Artinis) with an acquisition rate of 10 Hz. Our results showed large motor dual-task cost in seniors compared to young adults. Regarding hemodynamic activity, we have observed a prominent activation of the PFC in the young adults compared to the seniors during the dual-task condition.