The optimization of healthcare delivery, patient safety, and financial performance is crucial in the healthcare sector, driving the adoption of Lean healthcare methodology. This approach, centered on principles of waste elimination and value addition, has the potential to enhance patient care quality as Lean maturity increases. However, despite successful cases, criticisms have arisen regarding the effectiveness of Lean implementation in hospital environments. It is believed that the existence of underexplored obstacles could explain the slow adoption of the Lean culture in hospital organizations. Thus, it is considered essential to recognize and better understand these factors for a correct and efficient Lean implementation. In this context, this work proposes an evaluative Framework, from the Organizational Interoperability perspective, to enable hospitals to assess their Lean maturity and readiness for successful implementation. The Framework introduces a diagnostic evaluation and decision-making model for guiding Lean implementation based on three multicriteria decision support methods: Analytic Hierarchy Process and Decision Making Trial and Evaluation Laboratory for diagnostic evaluation, and Preference Ranking Organization Method for Enrichment Evaluation for decisional evaluation. Finally, the developed Framework will be applied to an Emergency Care Unit (ECU) undergoing a Lean implementation project. The Framework will enable the assessment of the ECU’s capacity to receive such implementation, the identification of obstacles, and their influence on the Lean action plan.