BACKGROUND:Self-care refers to behaviors that individuals adopt to prevent or maintain the stability of an illness (self-care maintenance), to monitor signs and symptoms (self-care monitoring), and to respond to signs and symptoms of an illness exacerbation (self-care management). A generic measure of self-care, the Self-Care of Chronic Illness Inventory, based on the Theory of Self-Care of Chronic Illness, was developed for use in individuals with any number and type of chronic conditions. OBJECTIVE:The current study investigated the measurement equivalence of the Self-Care of Chronic Illness Inventory in individuals from three different cultural groups. We were interested in determining if Italians, Swedes, and Americans interpret the measure in a conceptually similar way. METHODS:This cross-sectional study enrolled 1629 patients, 784 recruited in Italy, 438 in Sweden and 407 in the United States. Self-care (self-care maintenance, self-care monitoring and self-care management) was measured with the Self-Care of Chronic Illness Inventory. A multi-group confirmatory factor analytic approach was used to assess the equivalence of the measures across the three countries. Configural, metric, scalar and strict invariance were tested through a series of nested models where increasingly stringent equality constraints were posited. RESULTS:Participants were mostly males (56.3%), older adults (69.8%) and had at least two chronic conditions. Results indicated that three out of four measurement equivalence levels were partially or totally supported in all three of the Self-Care of Chronic Illness Inventory scales. The partial scalar invariance level was reached for self-care maintenance [χ2(50) = 63.495, p = 0.095; RMSEA = 0.022, p = 0.999, 90% CI = 0.000 0.038; CFI = 0.981; TLI = 0.977; SRMR = 0.036], self-care monitoring [χ2(22) = 28.770, p = 0.095; RMSEA = 0.024, p = 0.978, 90% CI = 0.000 0.046; CFI = 0.996; TLI = 0.995; SRMR = 0.054], and self-care management [χ2(51) = 91.334, p = 0.001; RMSEA = 0.048, p = 0.576, 90% CI = 0.031 0.063; CFI = 0.949; TLI = 0.937; SRMR = 0.047] scales. CONCLUSIONS:These findings suggest that patients in the three countries used an identical cognitive framework or mental model when responding and used the 1-5 Likert response scale in an almost identical way, almost without bias. In spite of sociocultural differences, patients in these countries seem to share the same fundamental view of self-care. The results of the Self-Care of Chronic Illness Inventory will be comparable in these countries.