The purpose of this study was to review the existing literature investigating carbohydrate mouth rinsing (CMR) as an ergogenic aid by using the effect sizes and percentage change in performance of the respective studies as outcome measures. A trivial-small average overall effect size was present for the 25 studies included in the review (0.18, 95% CI = 0.10 to 0.27). Effect sizes for the sub-groups were; ≥25-min (0.25, 95% CI = 0.14 to 0.36), ≤ 180 seconds (0.06, 95% CI = -0.03 to 0.15), resistance exercise (-0.09, 95% CI -0.20 to 0.03) but the effect size is still small. A sub-analysis of ~1-h cycling time trial performance resulted in an overall effect size of 0.20 (95% CI = 0.02 to 0.38), and effect sizes for performance time and power output of 0.31 (95% CI = -0.02 to 0.64) and 0.19 (95% CI = -0.09 to 0.46) respectively. Whilst effect sizes were small the average percentage change in performance in ~1-h trials was 2.48%, which may have implications for elite performers as this is greater than the 1.30% smallest worthwhile change recommended in past research.