Discharge planning is a continuous process to prepare post-hospitalization patients so they can carry out independent care. Nurse knowledge is one of the factors that influences the implementation of discharge planning. The research aims to analyze the relationship between the level of knowledge and the behavior of nurses in preparing discharge planning in inpatient rooms at private hospitals in Yogyakarta. This research uses descriptive analytical correlation with a cross sectional approach. Samples were taken using purposive sampling as many as 33 respondents with data analysis using the Spearman Rank test. The research instrument used questionnaires and observations of patient medical records. The research results showed that the level of nurses' knowledge regarding discharge planning was in the good category (76%). The behavior of nurses in preparing discharge planning was good (73%). Analysis between the level of knowledge and behavior of nurses in preparing discharge planning with a p value of 0.007 and strength of correlation (r) 0.460. There is a relationship between the level of knowledge and the behavior of nurses in preparing discharge planning. It is recommended that nurses increase their knowledge, especially in preparing patient discharge planning, by increasing their knowledge independently via the internet, attending training or seminars related to discharge planning.