Purpose The purpose of this study was to determine the effectiveness of six-weeks intermittent hypoxic training at 3,000 m hypobaric hypoxic condition on aerobic and anaerobic exercise capacity in competitive swimmers. Methods South Korean swimmers (n=20) were randomly assigned into training at sea-level (n=10, intermittent normoxic training group; INT) and training at 526 torr corresponding to 3,000 m hypobaric hypoxic condition (n=10, intermittent hypoxic training group; IHT). The participants completed an aerobic continuous treadmill training (30 min) within 80%HRmax and anaerobic interval bicycle training (10 times; 2 min of exercise and 1 min of rest) for 30min within 90%HRmax in each environment. We compared their aerobic and anaerobic exercise capacity before and after six-weeks of training. Exercise frequency was 1 hour, 3 days per a week, and during 6 week. Results In aerobic exercise capacity, PWC at 75%HRmax, estimated VO2 max, and exercise time were increased by training in only the IHT group. Estimated VO2 at 75%HRmax was increased by training in both groups, but presented a larger increase tendency in the IHT group compared with the INT group. In anaerobic exercise capacity, peak anaerobic power and fatigue index were increased by training in only the IHT group. Blood lactate level after wingate test were decreased by training in both groups, but the IHT group have a lower blood lactate level in after training compared with the INT group. Conclusion In our study, we did not measure to various dependent variables for support to enhancement of aerobic and anaerobic exercise performance. However, these results showed that the IHT method may be effective in improvement of exercise performance in competitive swimmers who participates in a variety of events from short to long distance.