CONTEXT AND OBJECTIVE: Diabetes is a public health problem and good glycemic control is able to prevent or contain its complications. Self-efficacy is a key factor in successfully achieving behavior goals. The aim of this study was to analyze the psychometric properties of the insulin management diabetes self-efficacy scale (IMDSES) on type 1 diabetes patients from southern Brazil. DESIGN AND SETTING: Validation study in two cities in southern Brazil. METHODS: The psychometric properties of IMDSES were evaluated in a population of type 1 diabetes patients (n = 213), from September to December 2004, who were attended within the Brazilian public healthcare system. Principal component analysis was conducted to develop the subscales. Cronbach’s alpha was used as the reliability coefficient. RESULTS: The analysis of psychometric properties resulted in an IMDSES consisting of 20 items and three subscales: diet (alpha: 0.83), insulin (alpha: 0.92) and general management (alpha: 0.78) and accounted for 53% of the variance. Criteria validity was investigated through two parameters: glycohemoglobin, which showed significant association with self-efficacy on the insulin subscale (p = 0.04), and the variable "adherence", which was significantly associated with self-efficacy on two subscales (p < 0.05). CONCLUSIONS: This study shows that the IMDSES is valid and reliable, and can be used to measure results from diabetes educational programs and to measure self-efficacy relating to diabetes management, for possible interventions.