Purpose: The purpose of this paper is to analyze the impact of learning in a project-driven organization and demonstrate analytically how the learning, which takes place during the execution of successive projects, and the forgetting that takes place during the dormant time between the project executions, can impact performance and productivity in the future. Design/methodology/approach: A learn-forget model was developed using the learning curve concept prevalent in many manufacturing processes. The model assumes that learning occurs while project tasks are being performed and forgetting takes place during dormant times between the successive implementations. The log-linear model was adapted, with both learning and forgetting rates being a function of the doubling or tripling of output. Forgetting is inhibited through the use of knowledge transfer tools such as use of close-out documents or content management platforms. The model is applied to a simulated project environment where a number of projects are executed sequentially, and the results are evaluated using the reduction in total duration and return on investment. Findings: Computational results demonstrate that the learning and forgetting rates and level of project close-out effort impact project performance, in the form of reduction in duration, much more significantly compared to the impact of the length of dormant times between the project initiations. Furthermore, even in a slow learning environment, using close-out reports as a knowledge transfer tool, managers can achieve more than a 40 percent reduction in duration after several successive implementations. Research limitations/implications: Although the theoretical development is applicable to a general organizational setting, the empirical testing of the model is done in project-driven organizations where projects are implemented on an ongoing basis. Practical implications: Managers can significantly benefit from the findings of this study. It is shown that the accumulated learning which represents knowledge generated during the implementation of a project, if transferred successfully, improves productivity and enables faster implementation. In a project-driven organization an almost 80 percent reduction in total duration is achievable with the use of close-out documents. This result promotes the importance of the learning process and managers should enable their team members to learn as much as they can while implementing a task and to document it methodically. Originality/value: This study constitutes an initial effort to illustrate quantitatively how the level of learning and forgetting impact performance in a project-driven organization. This study is also original in that it methodically demonstrates the importance of spending time during the phase-out, documenting the project artifacts, that enables knowledge transfer, and thus improves performance.