This study aimed to evaluate the effects of cardiorespiratory fitness (CRF) and mean arterial pressure (MAP) on the prefrontal cortex (PFC) oxygenation and dual-task performance in healthy young males. Changes in the concentration of oxygenated ($Δ$HbO2) and deoxygenated hemoglobin ($Δ$HHb) in the right and left PFC were examined during a cognitive auditory 2-back task. Cognitive performance (2-back task’s accuracy) and walking motor performances were measured in single-tasks (single motor and single cognitive) and dual-task (2-back task + walking). Thirty-six young males were ranked according to their V˙O2 peak. The second tertile was excluded to generate two groups of different CRF (high fit group: n = 12 and V˙O2 peak = 56.0 ± 6.7 ml kg−1 min−1; low-fit group: n = 12 and V˙O2 peak = 36.7 ± 4.1 ml kg−1 min−1). The CRF groups were further split into two subgroups according to 24-h MAP (higher-MAP, lower-MAP). Two-way ANOVA (CRF x n-back conditions) revealed a significant interaction between the CRF and cognitive task condition on 2-back accuracy (p = .007) and a main effect of CRF on ⊗HHb in the right and left PFC (p < .05). These results suggest that in healthy young males: 1) for CRF, only low-fit individuals demonstrate dual-task costs in accuracy (Dual < Single), and 2) that in comparison to the low-fit group, the high fit-group demonstrated greater changes in PFC oxygenation in $Δ$HHb, but not $Δ$HbO2.