Progressive developments in economics, society and politics have raised knowledge as a key element in development and competitiveness, and knowledge MANAGEMENT is considered to be an essential element in this field. By taking the temporary nature of the PROJECT into account, dynamics and competitiveness in PROJECT-oriented organizations within the business world make the preservation and MANAGEMENT of knowledge in PROJECT-based organizations more important. The lesson learned system is a knowledge MANAGEMENT tool that proposes strategic solutions that avoid wasting time and money and makes perfect use of knowledge MANAGEMENT accomplishments.Lessons learned (LL) systems have been deployed in many military, commercial, and government organizations to disseminate validated experiential lessons. They support organizational LL processes, and implement a knowledge MANAGEMENT (KM) approach for collecting, storing, disseminating, and reusing experiential working knowledge that, when applied, can significantly benefit targeted organizational processes. An effective lesson learned process can substantially improve decision processes, thus, representing an essential chapter in knowledge sharing and knowledge MANAGEMENT. Unfortunately, these systems typically fail to deliver lessons when and where they are needed.In this study, using a literature review, interviews and a case study, a roadmap for implementing the lesson learned system is explained in four stages. First, we illustrate the lesson learned and the learning in the PROJECT using a literature review. Second, we detail an understanding of commonly used methods in Iran obtained from two information sources; 1) interviews 2) a case study. Third, the information is analyzed and a conceptual model is developed based on the content analysis of data obtained in the second stage. Finally, we develop a roadmap by identifying key issues in the third stage and by adding activities and checklists to pursue its activities.This PROJECT learning roadmap assists business leaders in improving the lesson learned process. This model enables organizations to develop exclusive solutions tailored to the needs of the stakeholders.