This book constitutes the proceedings of the CVPR 2025 Challenge on Foundation Models for 3D Biomedical Image Segmentation, MedSegFM 2025, held in Nashville, TN, USA, during June 11–15, 2025.The 13 full papers included in this book were carefully reviewed and selected from 19 submissions. This conference provides state-of-the-art algorithms for biomedical image segmentation foundation models.