This systematic review explored the instruments used to measure Shared Decision Making (SDM) within long-term care (LTC) settings. Relevant publications from the period between January 2000 and October 2022 were searched across five databases. Thirty-six SDM assessment instruments were identified, which encompassed those measuring SDM for LTC recipients/family caregivers and/or healthcare providers. These instruments were either specifically tailored for LTC settings or more broadly applicable across healthcare contexts, including LTC. In terms of psychometric properties of the instruments, internal consistency reliability, content validity, structural validity, and hypothesis testing were commonly tested. The findings of this research can aid health researchers, managers, and scholars in choosing suitable instruments for assessing SDM in specific LTC scenarios, considering factors such as measurement scope, assessment methods, and instrument reliability. Additionally, these findings offer valuable insights for the future development of high-quality SDM assessment instruments in LTC field.