The pursuit of new implantation sites for transplantation of islets of Langerhans requires new experimental models. Since today's clinical islet transplantations to the liver show low success rates in part due to low revascularisation, we have developed a new in vivo-method for studying the revascularisation of islets transplanted to muscle. Mouse islets of Langerhans were isolated and syngeneically transplanted to the cremaster muscle or liver of mice. At different time-points post-transplantation the mice were anesthetized and the muscle was prepared for intravital and confocal microscopy. Revascularisation and microcirculation of the islets were examined and the graft-bearing organs were also retrieved and prepared for immunohistochemistry. Islets transplanted to the cremaster muscle had improved revascularisation compared to islets transplanted intraportally to the liver. Grafts in muscle had functional intra-islet vessels three days post-transplantation, whereas the newly formed vessels to the grafts in the liver instead surrounded the islet. Intravital microscopy of islets in the cremaster muscle revealed that leukocyte-endothelial cell interactions were increased in venules draining the transplanted islets compared to venules draining only the muscle. Emigrated leukocytes were also seen inside the grafts and in the adjacent tissue. In conclusion, the muscular site of engraftment was beneficial in terms of intra-islet revascularisation compared to the liver site. This new model offers a way to investigate pancreatic islet engraftment after transplantation to muscle in vivo. Vessel growth and -density are easily quantified and the model enables studies of the complex courses of events in graft angiogenesis, including contributions from different immune cell subsets.