Many companies have achieved significant results in recent decades by adopting the lean manufacturing philosophy, but its implementation still leaves room for improvement. The literature on this subject cites several critical processes during the implementation of lean projects that should be identified and improved to ensure even better results. This article aims to contribute to the aforementioned body of literature by assessing lean manufacturing projects using project management guidelines, specifically the 47 processes published in the 5th edition of the Project Management Body of Knowledge. Based on questionnaire-aided interviews with 17 professionals (eight corporate managers and nine experts with PhDs in this area), we found that the most critical processes in the implementation of lean projects involve procurement, stakeholder, communication, human resources, and risk management. The results presented here were validated using the techniques of multidimensional scaling, exploratory factor analysis, and descriptive statistics.84 22472256