Purpose: The National League for Nursing/Jeffries Simulation Theory (NLN/JST) is a middle-range theory widely used in nursing simulation education. Although the NLN/JST was revised in 2015, there is still no formal critique of the theory. The purpose of this study is to present a critique of the NLN/JST. Method: This study comprehensively analyzes and evaluates the theory using Fawcett and DeSanto-Madeya’s (2013) framework. Results: The theory demonstrates positive social and theoretical significance, testability, and empirical and pragmatic adequacy. Nevertheless, semantic clarity and internal consistency need to be made clearer. Conclusion: The NLN/JST is a suitable framework for nursing simulation education. The theory considers not only participants but also patients and systems as outcomes of simulation education, and is able to incorporate situation-specific backgrounds. That said, it is still necessary to develop a systematic nursing curriculum for clinical reasoning competence of both nursing students and nurses, given the wide range of clinical situations they may encounter.