This study aims to investigate and analyse organisational learning in project-based organisations (PBOs) that work with complex projects. The focus is to contribute to the knowledge about how PBOs can enhance the management of experiences derived from complex projects to promote organisational learning. This is investigated by studying how experience is captured and transferred within a project, across different projects, from project to the line organization and reintegrated into new projects. Additionally, the study examines challenges related to knowledge transfer and evaluates human and structural capital. To fulfil this, a case study is conducted on a consulting PBO that works with complex infrastructure projects. Qualitative interviews were conducted with individuals in various roles within the organisation. Furthermore, participant observations were conducted on meetings where project experience was discussed, both during ongoing projects and at project completion. The findings show that employees have a lot of knowledge and experience after working in complex projects. Experiences are collected and shared with other colleagues in various forums in complex projects. The findings suggest that PBOs can enhance their management of experiences from complex projects by the following strategies: (1) creating time for reflection to collect, discuss and evaluate experiences on an ongoing basis, (2) promoting knowledge exchange among colleagues to transfer tacit knowledge, (3) making documentation searchable and accessible beyond the project organization and (4) conducting regular and in-depth analysis to uncover patterns that can improve the structural capital. In future studies, it would be interesting to explore how artificial intelligence and machine learning could aid in conducting in-depth analysis of experiential data from complex projects. This to facilitate the identification of patterns and relationships within the data, providing valuable insight for enhancing organisational learning in PBOs.