Federated learning enables collaboration in medicine, where data is scattered across multiple centers without the need to aggregate the data in a central cloud. While, in general, machine learning models can be applied to a wide range of data types, graph neural networks (GNNs) are particularly developed for graphs, which are very common in the biomedical domain, e.g., for protein-protein-interaction (PPI) networks. Here, we present our ensemble-GNN library, which can be used to build federated, ensemble-based GNNs in Python. Ensemble-GNN allows to quickly build predictive models utilizing PPI networks consisting of various node features such as gene expression and/or DNA methylation. We exemplarily show the results from a public dataset of 981 patients and 8469 genes from the Cancer Genome Atlas (TCGA).