This book constitutes the refereed proceedings of the 9th International Workshop on Simulation and Synthesis in Medical Imaging, SASHIMI 2024, held in conjunction with the 27th International conference on Medical Image Computing and Computer Assisted Intervention, MICCAI 2024, in Marrakesh, Morocco in October 2024. The 19 papers included in this book were carefully reviewed and selected from 32 submissions. They focus on recent developments in methods for image-to-image translation, image synthesis, biophysical modelling, super-resolution and image segmentation and classification.