Abstract Aims This study aims to (i) test the validity and reliability of the Care Dependency Scale (CDS) for patients with heart failure (HF) and (ii) test the validity and reliability of the proxy version of the CDS assessing informal caregivers’ perception of the dependency level of individuals with HF. Methods and results Secondary data analysis was conducted of transnational multicentre cross-sectional design study. A convenience sample comprised of HF patients–informal caregivers’ dyads in three European countries. The CDS was administered to patients and the proxy version to informal caregivers. Factorial validity was tested for each scale using confirmatory factor analysis. Reliability was evaluated with the composite coefficient and Cronbach’s alpha. Construct validity was tested via known group differences. Measurement error was tested to assess responsiveness to changes. A total of 229 patients and 208 caregivers were recruited. Confirmatory factor analysis supported the two-factor structure (Physical Care Dependency and Psychosocial Care Dependency) of the CDS in both HF patients and their caregiver. Reliability estimates were adequate for all reliability coefficients. Construct validity was supported. The measurement error was adequate. Conclusion The scale shows acceptable validity and reliability and can be useful for care dependency assessment of patients with HF and their informal caregivers. Further research is needed for assessing the validity and reliability in other cross-cultural settings. The use of the CDS has the potential to effectively enable the development of pertinent care plans, taking dependency into consideration including the perspective of both members of the dyad as a whole.