Developers’ technical expertise is crucial for various tasks within open-source communities, such as identifying suitable maintainers or reviewers. However, GitHub, the world’s largest open-source code hosting platform, does not explicitly display developers’ technical expertise. Existing methods fail to fully capture the multifaceted and dynamic nature of their skills and knowledge. To address this problem, we propose a novel approach to derive developers’ technical expertise using graph neural networks (GNN). We construct a GitHub social network to integrate social and development activities and employ a GNN model to learn low-dimensional embedding for developers’ technical expertise. We verify the effectiveness of our model on four GitHub social relationship recommendation tasks. The results demonstrate that our approach performs well in predicting technical preference for repositories and developers.