Production of reactive oxygen species (ROS) during contractions is associated with muscular fatigue and damage in the short-term and adaptive responses in the long-term. When adaptation is inconsequential acute antioxidant supplementation may be able to attenuate muscle fatigue and damage to enhance performance. This study aimed to determine the effects of acute oral N-acetylcysteine (NAC) supplementation on Yo-Yo intermittent recovery test performance level one (YIRT-L1) following repeated-bouts of damaging intermittent exercise. In a pair-matched design, twelve recreationally-trained males engaged in either six days of NAC (n = 6) or placebo (n = 6) supplementation. Following a treatment loading day, participants completed three testing sessions, on alternate days, consisting of a pre-exercise Isokinetic dynamometry (IKD) test, a damaging intermittent exercise protocol, YIRT-L1 and a post-exercise IKD. A further IKD test was completed on the two intervening days. NAC treatment resulted in a significant preservation of YIRT-L1 performance (P≤0.0005). IKD performance significantly deteriorated over time at all contractions speeds and this deterioration was not influenced by treatment group. Plasma creatine kinase values increased significantly over time (P=.002) and were significantly greater in the NAC group compared with the placebo group (P=.029). NAC induced mild-gastrointenstinal side effects. NAC supplementation may be a useful strategy to enhance performance during short-term competitive situations where adaption is inconsequential. Titration studies to elucidate a treatment dose that enhances performance without inducing side-effects are now required.