Clinical tests for the evaluation of balance in people with intellectual disability that have been most commonly used depend on the subjective evaluation of the evaluator, easily reach the ceiling effect and are poorly sensitive to small changes; but new tests have been developed, such as the Six Spot Step Test. The aim of this study was to determine the validity and within-day and day-to-day test-retest reliability of the Six Spot Step Test in people with intellectual disability. A descriptive cross-sectional study was conducted with 18 people with intellectual disability. The participants conducted the Six Spot Step Test three times and a set of five clinical tests for the balance assessment. The relative reliability was excellent (Intraclass Correlation Coefficient (ICC) = 0.86 - 0.97), and the absolute reliability ranged between 4.7% and 7.3% for coefficient variation and between 0.6 and 1.2 for the standard error of measurement. Linear regression models showed that that test can explain the results of the Timed Up & Go, Four Square Step Test and the Berg Balance Scale. The Six Spot Step Test proved to be as valid and reliable for the evaluation of dynamic balance in people with intellectual disability as the most frequently used tests for the clinical evaluation of postural control.