Background: Hypertension disease found in Indonesia is mainly on the elderlys. Elderlys with hypertension have the risk to the quality of life. One way to control blood pressure by doing diet hypertension. Knowledge of the family played an important role towards on the elderlys hypertension diet support health. The purpose of the study: Find out the level of knowledge of the family in an effort at Posyandu Elderlys hypertension diet at Ngebel Tamantirto Kasihan Bantul of Yogyakarta. Research methods: The design of this research used quantitative descriptive with cross-sectional approach. The population in this research is 78 reponden. Sampling techniques used a purposive sampling with 50 number of respondents. Research instrument used questionnaire data demographics and family level of knowledge about the diet of hypertension in the elderlys. Study results: Most of the family's level of knowledge about the diet of hypertension in good categories to 82.4%, 36 people quite 18.0%, 9 people and less numbered 5 10.0%. Conclusion: Most of the respondents at the Posyandu Elderlys Ngebel Tamantirto Kasihan Bantul Yogyakarta have a good level of knowledge about the diet of hypertension.