Objectives: Self-efficacy is an important factor in the acquisition of self-management skills in patients with chronic diseases. The present study provides a translation and cultural adaptation for the Portuguese population, as well as psychometric properties, of the Self-Efficacy for Managing Chronic Disease 6-Item Scale. Materials and Methods: This is a cross-sectional study. As a first stage, a translation and cultural adaptation were conducted. After preparation, a final version was applied initially to a sample of 30 participants with chronic disease in two phases, with a one-week gap between phases, to assess teste retest reliability. Subsequently, a sample of 217 participants with chronic disease, mean age 42.8 (10.7) years, participated in the study. Participants were supposed to be over the age of 18 and with at least one clinically diagnosed chronic disease. The questionnaire was applied electronically. Results: The results showed a good test retest reliability (ICC of 0.83, 95% CI: 0.65 – 0.92). Internal consistency met the criterion for a reliable measure (global Cronbach’s alpha of 0.95). Item-total correlations of all items were above 0.30. A correlation matrix was considered favorable (KMO = 0.90; Bartlett's sphericity test = 1399.090, p < 0.01). The results confirmed the permanence of the 6 items, as in the original scale. Conclusions: A Self-Efficacy for Managing Chronic Disease 6-Item Scale is a reliable and valid instrument to assess the patients' self-efficacy for managing chronic diseases in Portuguese, enabling its use in clinical practice and in future studies.