Background: Carbohydrate (CHO) mouth rinse has been used as an ergogenic strategy due to its central effect; however, the effects of this intervention during short-duration high-intensity exercises are not fully understood. Purpose: To investigate the effect of CHO mouth rinse on time to exhaustion in a short-duration high-intensity exercise performed on a treadmill. Methods: A randomized double-blind, placebo-controlled, crossover study was conducted with 10 (24.1 [4.3] y) recreationally active male runners. The protocol consisted of a warm-up at 65% of VO2max for 5 min followed by 3 min passive rest. At the end of this rest period, the individuals performed their mouth rinse either with CHO (maltodextrin, 6%) or with placebo (industrialized noncaloric juice with the same taste). Immediately after mouth rinse, the subjects ran at velocity equivalent to 100% of individual VO2max until voluntary exhaustion. The perceived effort was obtained through a Borg scale. Blood lactate was quantified before and after the protocol, and heart rate was evaluated during the protocol. Results: No difference was found (P = .90) in time to exhaustion between placebo (193.9 [46.5] s) and CHO mouth rinse (195.1 [51.8] s). Blood lactate, heart rate, and perception of effort increased in both groups, but with no differences (all variables, P > .05) between groups. Conclusion: The findings showed that a preexercise single-CHO mouth rinse was ineffective to improve running time to exhaustion at velocity equivalent to 100% VO2max on a treadmill in recreationally active male runners.