International physical activity guidelines recommend that older adults accumulate 150 min/week of moderate-vigorous physical activity (MVPA). It is unclear whether meeting this recommendation is associated with better higher-order cognitive functions and if so, what are the neurophysiological mechanisms responsible for such a relationship. We tested the hypothesis that meeting MVPA guidelines is associated with better executive function in older adults, and explored if greater increases in prefrontal cortex oxygenation are implicated. Older adults who did (active, n = 19; 251 ± 79 min/week) or who did not (inactive, n = 16; 89 ± 33 min/week) achieve activity guidelines were compared. Executive function was determined via a computerized Stroop task while changes in left prefrontal cortex oxygenation ($Δ$O2Hb) were measured with functional near-infrared spectroscopy. Aerobic fitness (VO˙ 2peak) was determined using a graded, maximal cycle ergometry test. MVPA and sedentary time were objectively assessed over 5 days. Both groups had similar (both, P > 0.11) levels of aerobic fitness (24.9 ± 8.9 vs. 20.9 ± 5.6 ml/kg/min) and sedentary time (529 ± 60 vs. 571 ± 90 min/day). The active group had faster reaction times (1193 ± 230 vs. 1377 ± 239 ms, P < 0.001) and greater increases in prefrontal cortex $Δ$O2Hb (9.4 ± 5.6 a.u vs. 5.8 ± 3.4 a.u, P = 0.04) during the most executively demanding Stroop condition than the Inactive group. Weekly MVPA was negatively correlated to executive function reaction times (r = − 0.37, P = 0.03) but positively correlated to the $Δ$O2Hb responses (r = 0.39. P = 0.02) during the executive task. In older adults, meeting MVPA guidelines is associated with better executive function and larger increases in cerebral oxygenation among older adults.