The diagnosis of a chronic disease such as diabetes generally evokes strong emotions and often brings with it the need to make changes in lifestyle behaviours, such as diet, exercise, medication management and monitoring clinical and metabolic parameters. The diagnosis thus affects not only the person diagnosed but also the family members. Chronic illnesses are largely self-managed with approximately 99% of the care becoming the responsibility of patients and their families or others involved in the daily management of their illnesses. While the responsibility for outcomes, such as metabolic control and chronic complications, are shared with the health care team, the daily decisions and behaviours adopted by patients clearly have a strong influence on their future health and well-being. While diabetes self-management education is essential, it is generally not sufficient for patients to sustain behaviours and cope with a lifetime of diabetes. Peers have been proposed as one method for assisting patients to deal with the behavioural and affective components of diabetes and to provide ongoing self-management support. This paper first describes effective behavioural strategies in diabetes, based on multiple studies and/or meta-analyses, and then provides examples of their use by peers or in peer-based programmes in diabetes. A comprehensive search using the MEDLINE and Cinahl databases was conducted. Key search terms included peer mentors, peer leaders, peer educators, lay health workers and community health workers. Studies that clearly identified behavioural strategies used by peers were included.