Highly branched cyclic dextrin (HBCD) is a novel type of maltodextrin with a narrow molecular weight distribution that is produced from starch. In this study, we investigated the effects of HBCD administration on endurance performance. Seven elite swimmers participated in three trials, conducted in random order. In each trial, the subjects received either HBCD, glucose (1.5 g carbohydrate/kg body weight) or water (as a control), and immediately carried out 10 cycles of intermittent swimming consisting of 5 min of swimming at 75% followed by 3 min of rest, and subsequent swimming at 90% to exhaustion. The time to fatigue was about 70% longer in the HBCD trial than that in the glucose and control trials, a significant difference. Plasma glucose in the HBCD group was maintained at higher levels during pre-swimming cycles than that in the glucose or water group. These results suggest that HBCD administration enhances endurance performance.