D Diabetes mellitus is a disease caused by the disruption of glucose metabolism that fails body to control glucose obtained from foods. As the result, the glucose levels are raising. On the management of DM there are four main pillars include, namely diet planning. This study aims at finding out the correlation between knowledge of diet and dietary adherence in people with diabetes mellitus. This is an observational analytic research using cross-sectional method. It uses consecutive non random sampling technique involving 90 patients of diabetes mellitus in Pelni Hospital, Petamburan, West Jakarta as research subjects. The data are collected through filling out questionnaires about dietary knowledge and interviewing food recall questionnaires for 2X24 hours. The data are analysed using SPSS version 24 with 0.05 level of significant. The results reveal that among 90 respondents, 26 of them are at good level of knowledge and obedient while the other 19 are at good level of knowledge but not obedient. There are 10 respondents who have poor knowledge but are obedient and 54 respondents who are not obedient. The bivariate analysis of this research finds that there is correlation between knowledge of diet and dietary adherence in the patients of diabetes mellitus with P value = 0.001. There is correlation between knowledge level of diet and dietary adherence in the patients of diabetes mellitus.