Introduction: There are few studies carried out to assess the association between the level of knowledge about type 2 diabetes mellitus and the attitudes that patients have to improve the control of their disease. Objective: To determine the association between the level of knowledge and preventive attitudes about chronic complications in patients with type 2 diabetes mellitus. Methods: Analytical cross-sectional study in patients with type 2 diabetes in Chiclayo, Peru. The association between preventive attitudes and level of knowledge was investigated, as well as the association with age, sex, level of education, previous diabetic education, family history, previous hospitalizations, time of illness. Results: Of 150 patients, 60% were women. 40.0% presented an intermediate level of knowledge and 84.7% reported favorable preventive attitudes. It was found that patients with an adequate level of knowledge had a 43% higher frequency of presenting favorable preventive attitudes (Prevalence ratio = 1,43). Patients who had between 7 and 15 years of disease were positively associated with having favorable preventive attitudes (Prevalence ratio = 1,32). Conclusions: Diabetic patients with adequate knowledge about their disease have favorable preventive attitudes towards their condition and its chronic complications. In addition, patients diagnosed between 7-15 years ago have better preventive attitudes.