Objectives: The main objective was to identify the test-retest reliability of the Wii Balance Board (WBB) for assessing standing balance when administered to a population of people with intellectual disability (ID). A secondary objective was to provide information regarding the reliability of the WBB, taking into account the severity of cognitive impairment. Methods: The WBB was administered two times to a group of 50 people (mean age: 20.44 ± 5.73 years) with mild (n=32), moderate (n=6), or severe ID (n=12) within a 15-day period. The relative reliability of the WBB for the 'standing balance with open eyes' test was analyzed by means of intraclass correlation coefficients (ICCs). The standard error measurement and the minimum detectable change were used to identify absolute reliability. Results: For the whole sample, the WBB showed a fair (ICC=0.71), poor (ICC=0.66), and excellent (ICC=0.99) relative reliability for assessing weight-bearing asymmetry, center of pressure, path length, and sway area, respectively. In people with moderate/severe ID, statistically significant differences between the WBB test and retest scores were found. The absolute reliability of the WBB was considered poor. Conclusion: The WBB showed accurate adequate test-retest reliability for assessing standing balance in young people with ID. When using this device with people with moderate/severe ID, it is advisable to perform several testing trials, in order to avoid a possible learning effect. Standard error of measurement and minimal detectable change were high, indicating that this device might not be sensitive enough to properly identify static balance changes in this population.