BACKGROUND AND PURPOSE The purpose of this study was to document the psychometric properties of the Patient Activation Measure (PAM) in hospitalized multimorbid patients. METHODS Data from 313 patients were used for psychometric testing. RESULTS Estimated reliability of the PAM was .88; the content validity index was .91. Convergent and divergent validity with measures of physical functioning, depression, quality of care, severity of illness, and number of multimorbid conditions were confirmed. Confirmatory factor analysis did not support a good fit of the 1-factor model. CONCLUSION The PAM is a reliable and valid instrument to assess patient activation in hospitalized multimorbid patients. Further study is needed to determine what factors predict activation and how activation can assist in tailoring discharge planning.