Background: Transition in the health system is associated with the movement of the patient between clinical units and between hospitals, This is a complex process with several potential challenges including medical errors, adverse events, increased costs and patient dissatisfaction. Evidence shows that there is a need for greater clarity regarding the concept of transition. Objectives: The present Study was conducted to clarify the core elements of transition in patients admitted to the ICU.Methods: Walker and Avant's eight-step model was used to guide this concept analysis to provid a comprehensive definition of transition. A Literature search was conducted on CINAHL, Scopus, Pubmed, and Google scholar using the following keywords: transition, intensive care unit, transition care, patient transfer and transition process. Thus, after an extensive review of resources published in the years 2000-2020, articles related to this concept were examined based on the inclusion criteria. Definitions, properties, applications, consequences and empirical references of the concept of transition were extracted.Results: Transition is a complex, multifaceted concept with defining attributes: Critical points and events, disturb normal life, passage of change, instability and un-anticipated changes, Multiple needs, Inadequate continuity of care, Poor coordination of care and communication among health care providers, patients and families, multiple factor, multiple professionals, Awareness, Engagement And Adaptation. The differences in the response to transition according to the patient's condition or position (beliefs, attitudes, socioeconomic status, willingness and knowledge) and environmental conditions (the status of communication and support from the community) lead to the development of confidence, adaptation, recovery from critical illness and return to normal life or disability and other complications.Conclusion: The transition is a process of progressive change and the adaptation requires training and environmental changes to improve and develop new skills for transition. Nurses play a supportive and complementary role in successful transition of patients. Therefore, studies need to focuse on the evaluation of nurses' perceptions of patient transition and the consequences and outcomes. The result of this study provide a definition of transition that is relevant and useful for clinical research and practice in healthcare setting.