BACKGROUND: The CAregiver Perceptions About CommunIcaTion with Clinical Team members (CAPACITY) instrument measures how care partners perceive themselves to be supported by the patient's health care team and their experiences communicating with the team. OBJECTIVES: The objective of this study was to assess the measurement properties (ie, structural validity of the construct and internal consistency) of the CAPACITY instrument in care partners of patients with cognitive impairment, and to examine whether care partner health literacy and patient cognitive impairment are associated with a higher or lower CAPACITY score. RESEARCH DESIGN: This was a retrospective cohort study. SUBJECTS: A total of 1746 dyads of community-dwelling care partners and older adults in the United States with cognitive impairment who obtained an amyloid positron emission tomography scan. MEASURES: The CAPACITY instrument comprises 12 items that can be combined as a total score or examined as subdomain scores about communication with the team and care partner capacity-assessment by the team. The 2 covariates of primary interest in the regression model are health literacy and level of cognitive impairment of the patient (Modified Telephone Interview Cognitive Status). RESULTS: Confirmatory factor analysis showed the CAPACITY items fit the expected 2-factor structure (communication and capacity). Higher cognitive functioning of patients and higher health literacy among care partners was associated with lower communication domain scores, lower capacity domain scores, and lower overall CAPACITY scores. CONCLUSIONS: The strong psychometric validity of the CAPACITY measure indicates it could have utility in other family caregivers or care partner studies assessing the quality of interactions with clinical teams. Knowing that CAPACITY differs by care partner health literacy and patient impairment level may help health care teams employ tailored strategies to achieve high-quality care partner interactions.