Grip strength is an important predictor of several health outcomes in the general older population. Grip strength assessment is feasible and reliable in older adults with intellectual disabilities (ID), which makes it a valuable measurement for application in this population. The purpose of this study was to investigate the effect of handedness on grip strength in the older population with ID. Handedness and grip strength were assessed in a sample of 1050 older adults (greater than or equal to 50 years) with borderline to profound ID. Results showed that 26.2% of the study sample was left-handed. In right-handed participants the dominant hand (right) was on average 8.7% stronger than the non-dominant hand (p less than 0.001). For lefthanded participants there was no significant difference between the dominant hand (left) and nondominant hand. However, more detailed analyses revealed that 34.5% of the participants were stronger with their non-dominant hand, (on average 16.6% stronger for right-handed and 16.3% stronger for left-handed participants). Because of the large strength ratios, distributed in favor of both the dominant as the non-dominant hand, it is recommended to assess both hands to get a valid result of grip strength in older adults with ID. (Contains 4 tables.)