Background: Spasticity in the upper limb is common after acquired brain impairment and may have a significant impact on the ability to perform meaningful daily activities. Traditionally, outcome measurement in spasticity rehabilitation has focused on impairment, however, improvements in impairments do not necessarily translate to improvements in an individual's ability to perform activities or engage in life roles. There is an increasing need for outcome measures that capture change in activity performance and life participation. Methods/Design: We will conduct a systematic review of the psychometric properties of instruments used to measure upper limb functional outcomes (activity performance and participation) in patients with spasticity. Assessments (n = 27) will be identified from a recently published systematic review of assessments that measure upper limb function in neurological rehabilitation for adults with focal spasticity, and a systematic review of each assessment will then be conducted. The databases MEDLINE, CINAHL and EMBASE will be searched from inception. Search strategies will include the name of the assessment and the COnsensus-based Standards for the selection of health status Measurement INstruments (COSMIN) published search strategy for identifying studies of measurement properties. The methodological rigour of the testing of the psychometric quality of instruments will be undertaken using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) checklist. International Classification of Functioning, Disability and Health (ICF) definitions of impairment, activity and participation will be used for content analysis of items to determine the extent to which assessments are valid measures of activity performance and life participation. We will present a narrative synthesis on the psychometric properties and utility of all instruments and make recommendations for assessment selection in practice. Discussion: This systematic review will present a narrative synthesis on the psychometric properties and utility of assessments used to evaluate function in adults with upper limb focal spasticity. Recommendations for assessment selection in practice will be made which will aid clinicians, managers and funding bodies to select an instrument fit for purpose. Importantly, appropriate assessment selection will provide a mechanism for capturing how applicable to everyday life the outcomes from individualised rehabilitation programs for the upper limb really are.