This case study investigates the crucial role of stakeholder management in the success of Lean Manufacturing projects, focusing on a metal-mechanic company that sought to optimize its operational efficiency and increase productivity through a consulting program. Given the existing gap in the literature regarding the influence of stakeholder engagement on the outcomes of Lean projects, this study seeks to answer the following question: How do stakeholder engagement and management influence the results of Lean Manufacturing consulting projects for metal-mechanic industries? The research employed a qualitative methodology, analysing the implementation of Lean practices and the engagement of stakeholders in all phases of the project. The main results demonstrate that the active involvement of stakeholders, through workshops and Lean tools, was fundamental to achieving a 49.8% increase in productivity and a 51.3% reduction in movement. The study concludes that effective stakeholder management and the promotion of a culture of continuous improvement are essential for the success of Lean Manufacturing projects, highlighting the importance of aligning project objectives with the needs and expectations of stakeholders.