OBJECTIVE: Although there is scientific evidence that stress adversely affects metabolic control, only a few studies have examined the role of stress management in improving glycemic control in patients with type 2 diabetes mellitus (DM). In this study, we investigated the effect of a relaxation technique on levels of stress and glycemic control. DESIGN: A total of 53 patients with type 2 DM were randomly assigned to undergo either an 8-week stress management program, consisting of 10 min of diaphragmatic breathing and 15 min of progressive muscle relaxation twice per day (n=25, intervention group), or not (n=28, control group). Perceived stress, health locus of control and HbA1c were primary outcomes and were measured before and after intervention. RESULTS: In the intervention group, perceived stress score (PSS) and HbA1c had decreased significantly (P<0.05) by the end of the program. Specifically concerning the PSS, the higher the initial levels of perceived stress the greater the benefit of the intervention. No other significant changes were found. CONCLUSIONS: Our results show a beneficial role of stress management for patients with type 2 DM, as regards both stress levels and glycemic control. It is recommended to consider this type of treatment as an adjunct to conventional therapy. We deem that our study could encourage future studies in this area with larger samples, longer duration and more objective measurements.