The lack of oxygen supply to the highly metabolic pancreatic islet cells is one of the major factors contributing to the failure of islet transplantation devices designed to cure type I diabetes (T1D). Several approaches to improve oxygenation in these devices have been developed. However, the lack of available technologies to provide reliable pO2 assessment in and around devices hinders the progress severely. We performed in vivo oxygen imaging of cell loaded encapsulation devices using pulse electron paramagnetic resonance oxygen imaging (EPROI) technique. For the first time, whole-body EPROI is used to monitor pO2 of implanted devices in this work.