Little is known about the effect of using an attentional focus instruction on motor performance in people with intellectual disabilities. Therefore, this study explored the effects of different attentional focus instructions on gross motor skill performances in individuals with Down syndrome. Seven community-dwelling participants (age 25.2±3.2 yrs, height 1.70±0.04 m, body mass 72.0±6.3 kg) voluntarily participated in the study. Motor performance on 5-meter running (5m sprint), vertical jump (countermovement jump with arm swing, CMJ), broad jump (standing broad jump, SBJ), forward medball throw (FMBT) or overhead medball backward throw (OMBT) and rising-up from a chair (five repetition sit-to-stand, 5STS) were recorded while performing internal-focus (IF) or external-focus (EF) instructions. EF induced significantly (p<0.05) better performance than IF in CMJ (EF: 15±9 cm; IF: 11±8 cm, median ±interquartile range), SBJ (EF: 0.8±1.05 m; IF: 0.5±1.0 m), FMBT (EF: 1.5±1.4 m; IF: 1.4±1.1 m), OMBT (EF: 4.0±1.5 m; IF: 3.6±1.1 m) and 5STS (EF: 14.2±5.4; IF:15.3±7.7 s). The time over the 5m sprint tended to be shorter with EF (4.0±2.0 s) than IF (5.05±3.3 s) but the difference did not reach the statistical significance (p = 0.29). Physical trainers and school teachers should be encouraged to manage different types of attentional focus instructions to improve cognitive and gross motor performances in persons with Down syndrome.