The purpose of this study was to develop an instant MR cell labeling technique, called magnetosonoporation. First, a magnetosonoporation apparatus was successfully established for MR labeling of stem cells. Then, the safety of this new cell labeling approach was confirmed by evaluation of cell viability, proliferation, and differentiation of magnetosonoporation-labeled and unlabeled C17.2 neural stem cells. Subsequently, the feasibility of using in vivo MRI to detect magnetosonoporation/Feridex-labeled stem cells was validated in living animals and confirmed by histologic correlation. The magnetosonoporation technique is expected to be convenient, efficient, and safe for future clinical application of MRI-guided cell therapies.