The Roy Adaptation Model (RAM) focuses on the physiological and psychosocial adaptation of patients to the environment by using the four adaptive modes: physiologic, self-concept, role function, and interdependence. Aim: To evaluate the effect of the (RAM) application on patients undergoing hemodialysis. Subjects and method: Design: One group quasi-experimental design (pre and post) was used in this study. Setting: This study was conducted at hemodialysis unit of General hospital in Port Said city. Subjects: The study data was collected from purposive adult patients undergoing hemodialysis (no=105) in 9 months. Tools: two tools were used, tool I: includes structure interview questionnaire, Tool II: designed model based on RAM tools.  Results: There was an observed improvement in mean ±SD of total RAM modes 246±39.2 post model implementation compared to 218±40.3 pre- model implementation. There was a statistically significant difference for the mean scores of RAM modes of patients (physiological, self-concept, work role function, and independence and interdependence mode) on pre and post-application of RAM. Conclusion: There was a statistically significant difference for the mean scores of physiological, self-concept, work role function, and independence and interdependence mode of patients on pre and post-application of RAM. There was observed improvement in adaptation level among patients undergoing hemodialysis after application of RAM, especially in Independence and Interdependence mode. Recommendations: Encourage further study on theory-based patient care for chronic and acute illnesses. Encourage effective utilization of research findings on the management of diseases affecting hemodialysis patients.