Background: nursing students are required to think reflectively in both real and simulated clinical practice. Although the Reflective Thinking instrument is reliable in its measurement of reflective thinking, its validity is unknown. Method: confirmatory factor analysis was undertaken in an iterative manner within a non-equivalent control-group study to measure nursing students’ reflective thinking and satisfaction with high-fidelity simulation. The validity and reliability of the Reflective Thinking instrument was tested. Results: the resulting instrument consisted of 15 items across four factors. The (...) final model was plausible as it demonstrated ‘goodness of fit’; however, it had neither convergent or discriminatory validity, nor reliability. Internal consistency was fair to reasonable for the four subscales. Conclusion: the testing of the Reflective Thinking instrument using confirmatory factor analysis is a vital initial step in the modification of this instrument. Further development using exploratory factor analysis will enhance the instrument’s relevance within high-fidelity simulation. (shrink)