Purpose This paper aims to study the challenge of transferring knowledge among product development processes of an research and development department and other departments of the organization. To have a more concise focus on this broad field and having a lean perspective, this paper aims to analyse and identify how the cross-training employee lean tool affects the knowledge transfer processes in the previously mentioned departments. Design/methodology/approach This paper bases its research on a valid theoretical framework which is built to develop an explorative perspective that allows the authors to create and interpret the data collected from the companies through interviews. The paper uses a qualitative perspective by using the expertise of the companies not only to validate and draw conclusions from the studied theoretical framework but also to look beyond it. Findings The companies agree that the implementation of the cross-training employee lean tool will have a positive effect on the knowledge transfer processes in the organizations. Other important advantages that are detected are that this lean tool broadens the knowledge and the competences of employees, and that it helps the company to manage the tacit knowledge. However, some unexpected drawbacks such as the lack of metrics for measuring the knowledge transfer and the strictness of this lean tool were also found. Originality/value No previous research exists that analyses the effect of cross-training lean tool in knowledge transfer processes. This paper identifies such a gap in the literature and is used as the starting point to motivate the use of this tool to improve knowledge transfer processes due to the positive effects of it.