Many athletes avoid using mouthguards because they believe that they impair their ability to breath and negatively affect performance. Recently, some manufacturers have developed "vented" mouthguards (VentMGs) to address this concern. The purposes of this investigation were to describe the impact of a commercially available "vented" boil-and-bite mouthguard on the physiological responses to graded exercise and to determine whether the use of the same mouthguard influences performance during traditional physical agility tests. Recreationally trained males (n = 15) (age = 24 ± 1 year; (Equation is included in full-text article.)= 43.5 ± 1.9 ml·kg·min; body mass index = 25.2 ± 0.9) completed 3 randomly assigned trials where they wore no mouthguard (control), a traditional mouthguard (TradMG), or a VentMG. During each trial, subjects completed a modified maximal exercise test on a cycle ergometer and a series of physical agility tests (40-m dash, vertical leap, broad jump, 3-cone drill, and shuttle run). No differences were seen between control and the TradMG in any cardiorespiratory measures at any time during the maximal exercise test. Ventilation and blood lactate were lower (p ≤ 0.05) during VentMG at 200 W and at MAX; however, no differences in (Equation is included in full-text article.)were observed. Although TradMG had no impact on physical agility, VentMG produced a higher (1.9 cm; p = 0.03) vertical leap than control. Both mouthguard conditions negatively affected perceptions of breathability, comfort, and ability to communicate, but no differences existed between the 2 conditions. These findings confirm that TradMG has no negative impact on physiological function during exercise and physical agility; however, VentMG may have a positive impact at higher workload and on vertical leap.