The purpose of the study was to investigate the effect of upper extremity (UE) weight bearing on UE impairment functional performance of persons with acquired brain injury (BI). A quasi-experimental design was used to examine a convenience sample of 99 persons with acquired BI and 22 without BI (WBI) living in a community re-entry centre. A computerized force-sensing array pressure map system was used to determine the UE pressure during unilateral and bilateral conditions. Differences between groups were examined using t-tests. Correlations were computed between UE weight bearing and hand function, and functional performance as measured by the Fugl-Meyer scale and functional independence measure (FIM) scale. The group of people with BI exerted significantly lower UE weight bearing during unilateral conditions as compared with persons WBI [left: t (119) = 2.34, p = 0.021; right: t (119) = 4.79, p = 0.043). UE weight-bearing measures correlated strongly with FIM motor scores with bilateral UE conditions yielded the highest significant correlation (bilateral left r = 0.487, p < 0.001; bilateral right r = 0.469, p < 0.01). The results indicated that UE weight-bearing pressure differs in unilateral and bilateral conditions, between persons with and WBI and between persons with stroke and traumatic brain injury. These findings may have implications for occupational therapists that use unilateral versus bilateral motor training for rehabilitation. There is a need to replicate the study design with a randomized and stratified sample of persons with BI.