Learning is crucial for project-based organisations to improve and survive. As reflection is essential for learning in and between projects, this article examines how reflection unfolds and under which conditions it can act as a project learning mechanism. Using five gate reviews at a Dutch contractor as an embedded single case study, we show that reflection is necessary for but cannot guarantee the learning in and between projects. Reflection is emerging from and embedded in the specific context of interpersonal project work. This reflection-for-action stimulates the learning for the ongoing project, incorporates experience made in previous projects, and draws implications for future projects. However, for reflection to become a project learning mechanism, the reflection process needs to proceed to later phases and higher intensities which depends on the relevance of the project issue at hand, the motivation of project team members to discuss this issue, and the reflection support they receive.