Habitually active adults (ACT) typically exhibit lower postprandial lipemia, a condition that may attenuate oxidative stress and endothelial dysfunction following a high-fat meal (HFM), compared with inactive adults (INA). Our objective was to compare triglycerides (TAG), superoxide dismutase activity (SOD), oxidative stress (thiobarbituric reactive substances; TBARS), and brachial artery flow-mediated dilation (FMD%) before and after an HFM challenge in ACT and INA. ACT (n = 7) and INA (n = 7) subjects were matched for body mass index, age, and sex. Plasma TAG, SOD, TBARS, and FMD% were measured at baseline and 4 h after an HFM challenge. TAG significantly increased following the HFM in INA (4.15 ± 3.79 mmol·L(-1) vs. 8.07 ± 5.12 mmol·L(-1)) and in ACT (2.16 ± 0.55 mmol·L(-1) vs. 3.24 ± 1.40 mmol·L(-1)). Baseline TBARS were greater in ACT and remained unchanged in response to the HFM in both INA (5.1 ± 2.7 mmol·L(-1) vs. 6.9 ± 2.9 mmol·L(-1)) and ACT (8.6 ± 2.0 mmol·L(-1) vs. 7.9 ± 1.9 mmol·L(-1)). ACT exhibited greater SOD than INA at baseline (8.6 ± 0.7 U·mL(-1) vs. 7.8 ± 0.6 U·mL(-1)) and following the HFM (9.3 ± 1.2 U·mL(-1) vs. 8.0 ± 0.7 U·mL(-1)). Postprandial FMD% was decreased in INA (9.1% ± 4.0% vs. 6.2% ± 3.4%), yet remained unchanged in ACT (7.9% ± 3.7% vs. 9.3% ± 3.2%). In conclusion, the differential responses following an HFM support the concept that habitual physical activity can attenuate the negative postprandial alterations that affect vascular health.