Objective: To assess the construct, concurrent, and predictive validity of dynamic computerized hand dynamometry. Design: Prospective correlational study between dynamometry and functional upper limb performance. Setting: Hospital outpatient spasticity clinics. Participants: Adults with upper motor neuron syndrome affecting the upper limb after acquired brain injury (ABI) (n=38; median age, 50y; range, 18-81y) and healthy adult control participants (n=27; median age, 37y; range, 22-62y). Intervention: Not applicable. Main Outcome Measures: Dynamic computerized dynamometry elements of hand performance (isometric force, force velocity, isometric grip work, contraction and relaxation duration) and the Action Research Arm Test. Results: Motor elements of hand performance objectively measured by the dynamic computerized dynamometry protocol achieved moderate to good validity when correlated with standardized measures of functional hand performance. Dynamic computerized dynamometry identified clear differences in hand performance between participants with and without ABI. Within the ABI group, dynamic computerized hand dynamometry achieved fair to moderate predictive validity with regards to whether a participant would be referred for botulinum toxin A injections. Conclusions: This study provides support for the construct, concurrent, and predictive validity of the dynamic computerized dynamometry protocol.