Background: Caring code is a guidance developed as a guideline in applying caring behavior. Objects: to develop caring code in the Emergency Room of Universitas Sumatera Utara Hospital. Methods: The research used action research method. It was done from October, 2017, November, 2018, until January, 2019 through action research cycle 1. The research instrument was focus group discussion (FGD) guideline, questionnaires on nurses’ knowledge of caring, and observation sheets about nurses’ caring behavior. The samples were 20 nurses as the respondents, taken by using purposive sampling technique. The data were gathered qualitatively, using content analysis and quantitatively, using frequency distribution. Results: The result of the research showed that there were some themes: the meaning of caring according to the nurses, nurses’ caring behavior needed in the emergency, nurses’ caring behavior used by patients, the factors which influenced nurses’ caring behavior, and nurses’ obstacles in doing caring behavior. The caring code in the emergency room was divided into three stages, organized based on triage at Universitas Sumatera Utara Hospital which had 21 nurses’ caring behaviors. It increased nurses’ knowledge of caring: in the pre-caring code implementation, their knowledge frequency was 90%, and in the post-implementation it increased to 100%. In the pre-implementation, their caring behavior in the emergency room was60%, and in the post-implementation it increased to 90%. Conclusion: It is recommended that the hospital management give support and reward to nurses in the emergency room who have had good caring behavior.