This book constitutes the proceedings of the First International Workshop on Efficient Medical Artificial Intelligence, EMA4MICCAI 2025, held in conjunction with MICCAI 2025, in Daejeon, South Korea, on September 23, 2025.The 36 full papers included in this book were carefully reviewed and selected from 40 submissions. The EMA4MICCAI Workshop focuses on advancing computational effciency in medical AI by exploring innovative techniques such as lightweight model architectures, resource-conscious deployment strategies, and energy-effcient computing.