This descriptive cross-sectional study was conducted from March to November 2007 at a research and community services center of a Brazilian university. It aimed to explore the knowledge and attitude of people with diabetes mellitus who were attending a diabetes self-care education program. The sample was composed of 82 adults with diabetes mellitus. Data were collected through the Portuguese versions of the Diabetes Knowledge Questionnaire (DKN-A) and the Diabetes Attitude Questionnaire (ATT-19). Results revealed that 78.05% of the participants obtained scores higher than eight on knowledge about diabetes, which indicates they have knowledge and understand the disease. Scores on attitude ranged from 25 to 71 suggesting difficulty in coping with the disease. We conclude that although participants obtained a good score on knowledge, their attitude did not change so as to more adequately cope with the disease.