In addition to cognitive impairment, young adults with intellectual disabilities (IDs) are also more likely to be in poor health. Exercise may help ameliorate both of these deficits. While the health benefits of exercise are well documented and understood, the cognitive benefits of exercise are emerging. Exercise has been shown to improve the cognitive function of young, old, and diseased populations but few studies have evaluated the effect of exercise training on the cognitive functioning of individuals with IDs. The purpose of this study was to determine the effect of moderate-intensity exercise training on the cognitive function of young adults with IDs. Fourteen students (age, 19.4 ± 1.3 years) with mild to moderate IDs participated in an 8-week comprehensive exercise intervention program based on circuit training, aerobic dancing, and adapted sport activities. Sessions lasted 45 minutes, and intensity was maintained at 60-70% of maximum heart rate (HR(max)). Aerobic fitness was assessed via the Young Men's Christian Association (YMCA) step test, and intellectual functioning was assessed via 3 subtests from the Woodcock-Johnson III Tests of Cognitive Abilities once before and after the intervention. Performance was significantly improved on all 3 cognitive tests (all, p < 0.002). Aerobic fitness also significantly improved (p < 0.002). The mean percent increase in processing speed, a measure taking into account each individual's performance on the 3 subtests, was 103%. The mean individual improvement in aerobic fitness was 17.5%. Moderate-intensity exercise training can yield robust improvements in the cognitive functioning and aerobic fitness of young adults with IDs. These effects support the inclusion of exercise into the lives of young adults with ID to promote their physical and cognitive health. Fourteen students (age, 19.4 ± 1.3 years) with mild to moderate IDs participated in an 8-week comprehensive exercise intervention program based on circuit training, aerobic dancing, and adapted sport activities. Sessions lasted 45 minutes and intensity Powered by Editorial Manager and Preprint Manager from Aries Systems Corporation was maintained at 60-70% of HR(max). Aerobic fitness was assessed via the YMCA step test, and intellectual functioning was assessed via 3 subtests from the Woodcock-Johnson III Tests of Cognitive Abilities once before and after the intervention. Performance was significantly improved on all 3 cognitive tests (all, p < 0.002). Aerobic fitness also significantly improved (p < 0.002). The mean percent increase in processing speed, a measure taking into account each individual's performance on the 3 subtests, was 103%. The mean individual improvement in aerobic fitness was 17.5%. Moderate-intensity exercise training can yield robust improvements in the cognitive functioning and aerobic fitness of young adults with IDs. These effects support the inclusion of exercise into the lives of young adults with ID to promote their physical and cognitive health.