Aim The aim of this study was to compare the oxygen cost (V̄O2) of walking and running, as well as aerobic fitness, in children with and without developmental coordination disorder (DCD). Method Thirty-one males (17 with DCD and 14 in a comparison group; mean age 8y 7mo, SD 1y 3mo and 8y 5mo, SD 1y 2mo respectively) were tested on two separate occasions at least 1 week apart. On the first visit, motor proficiency was assessed by the McCarron Assessment of Neuromuscular Development instrument, which was followed by the determination of maximal aerobic capacity (V̄O2max). The second visit involved 4-minute bouts of treadmill walking (at 4.3km/h and 5.8km/h) and running (at 7.8km/h and 8.4km/h). Oxygen consumption, heart rate, respiratory exchange ratio, rating of perceived exertion (RPE), step rate, and qualitative assessment of locomotion were obtained for each speed. Results Despite poorer locomotion proficiency, there was no significant difference in the oxygen cost of walking or running between males with and without DCD. However, the DCD group had significantly higher RPE while running at 7.8km/h (p=0.011) and had greater difficulty achieving V̄O2max, resulting in significantly lower scores for aerobic fitness. Interpretation The differences in locomotion proficiency between children with and without DCD are not large enough to affect the oxygen cost of locomotion. However, children with DCD are more likely to withdraw from exercising at higher intensities before achieving peak performance.