BACKGROUND AND AIMS: Heart failure, insulin resistance and/or type 2 diabetes mellitus coexist in the syndrome that is diabetic cardiomyopathy. Patients with diabetic cardiomyopathy experience high symptom burden and poor quality of life. We tested the hypothesis that a low carbohydrate diet improves heart failure symptoms and quality of life in patients with diabetic cardiomyopathy. METHODS AND RESULTS: We conducted a 16-week randomised controlled pilot trial comparing the effects of a low carbohydrate diet (LC) to usual care (UC) in 17 adult patients with diabetic cardiomyopathy. New York Heart Association classification, weight, thirst distress and quality of life scores as well as blood pressure and biochemical data were assessed at baseline and at 16 weeks. Thirteen (n = 8 LC; n = 5 UC) patients completed the trial. The low carbohydrate diet induced significant weight loss in completers (p = 0.004). There was a large between-group difference in systolic blood pressure at the end of the study (Hedges's g 0.99[-014,2.08]). There were no significant differences in thirst or quality of life between groups. CONCLUSION: This is the first clinical trial utilising the low carbohydrate dietary approach in patients with diabetic cardiomyopathy in an outpatient setting. A low carbohydrate diet can lead to significant weight loss in patients with diabetic cardiomyopathy. Future clinical trials with larger samples and that focus on fluid and sodium requirements of patients with diabetic cardiomyopathy who engage in a low carbohydrate diet are warranted. CLINICAL TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trial Registry (ANZCTR): ACTRN12620001278921. DATE OF REGISTRATION: 26th November 2020.