Consumption of fish oil (FO) is associated with reduced adverse cardiovascular events. In a randomized, blinded, placebo-controlled trial, 26 subjects (17 men and 9 women; mean age [+/- SD] 31 +/- 3.7 years) received 1 g FO capsule (n = 14) or placebo (1 g of corn oil, n = 12) for 14 days. At day 0 and day 14, heart rate (HR), blood pressure, endothelium-dependent brachial artery flow-mediated vasodilation (EDV), and endothelium-independent nitroglycerin-mediated vasodilation (EIDV) were assessed with ultrasound. FO supplementation resulted in a significant increase in EDV (20.4% +/- 13.2% vs 9.9% +/- 5.4%; P = .036) and EIDV (32.6% +/- 16.8% vs 18.0% +/- 14.9%; P = .043). Resting HR decreased by a mean of 5.9 +/- 9.4 bpm (FO) compared with placebo (mean increase of 0.73 +/- 4.8 bpm [P = .05]). FO supplementation in healthy subjects is associated with improved endothelial function and decreased resting HR.