Background: Diabetes mellitus (DM) is one of the most chronic diseases suffered by many people in the world. One of the DM management is diet. Management in handling the diet DM, there are some obstacles such as lack of family support. Family support is one factor in diabetic patient to behave well in DM diet therapy. Objective: This study aimed to analyze the relationship between family support with the behavior of the DM patient's diet. Methods: This study was a correlational study with cross sectional approach. This research was conducted in June 2016. The sample in this study was 48 DM patients in Puskesmas Gamping Sleman 1 Yogyakarta which were selected using total sampling technique. Results:The results showed that the majority of family support was good (91.7%), and the behavior of diet was good (81.3%). The data was collected by using questionnaires and was analyzed by using Kolmogorov-simirnov test with p<0,05. There was no relationship between family support and dietary behavior among patients (p=0,223). Conclusion: There is no significant correlation between family support with the behavior of the DM patient's diet. Further researchers are suggested to analyze other factors that influence the behavior of the DM patient's diet and family support