Purpose: A routine preoperative assessment is considered both ineffective and inefficient. Despite the widespread application of lean thinking in healthcare, there is little evidence of successful experiences in preoperative admissions in order to reduce “No value added” activities. A conceptual framework reporting the drivers (clinic, tools, innovation, organization, and governance) and impacts (patient, efficiency, sustainability, time, learning and growth) was developed. Methodology: Drawing on the experience of an Italian high complexity hospital, this paper analyzes the case study by reporting evidence on how to implement lean in preoperative assessment and how to evaluate the positive results obtained. Results: Applying lean principles, the identification of value improved the appropriateness of care by creating 40 personalized pathways; the value stream resulted in a reduction of “No Value Added Time” from 37% to 28%, chest X-rays from 41% to 14% and cardiac visits from 49% to 37%; the pursuit of continuous flow through innovation contributed to increase the use of digitalization; the new pull organization helped to reduce the average time spent per year by 1.5 h; the continuous improvement was ensured through the governance of results. Conclusion: The proposed framework should be used to improve the quality of care in preoperative admissions by adopting the lean drivers for successful implementation and reporting the impacts.