This study investigates the psychometric properties of the Mutuality Scale in a sample of patient-caregiver dyads following a recent episode of coronary heart disease. A cross-sectional analysis was conducted. Factorial validity was tested with confirmatory factory analysis. Internal consistency reliability was investigated with the model-based internal consistency reliability index. Pearson's correlation coefficient was used to test convergent validity between mutuality and other theoretical and empirical variables associated with it. We included 150 patient-caregiver dyads (patient: mean age 65 years, 77% males, 71% married
caregiver: mean age 54 years, 21% males, 71% married). The CFA testing the theoretical four-factors (love, shared pleasurable activities, shared values, and reciprocity) of mutuality demonstrated adequate fit to the data in both the patient and caregiver version of the scale. Reliability estimates were adequate for the whole scale (model-based internal consistency index = 0.95). Significant positive correlations were observed between mutuality and self-care behaviors, and caregiver preparedness, supporting convergent validity. The Mutuality Scale demonstrated satisfactory structural and convergent validity and reliability in patient-caregiver dyads after the onset of a coronary heart disease event.