Microscopic examination of transplanted islets in an ectopic environment provides information to evaluate islet engraftment, including revascularization and reinnervation. However, due to the dispersed nature of blood vessels and nerves, global visualization of the graft neurovascular network has been difficult. In this research we revealed the neurovascular network by preparing transparent mouse islet grafts under the kidney capsule with optical clearing to investigate the sympathetic reinnervation via 3-dimensional (3D) confocal microscopy. Normoglycemic and streptozotocin-induced diabetic mice were used in syngeneic islet transplantation, with both groups maintaining euglycemia after transplantation. Triple staining of insulin/glucagon, blood vessels, and tyrosine hydroxylase (sympathetic marker) was used to reveal the graft microstructure, vasculature, and sympathetic innervation. Three weeks after transplantation we observed peri-graft sympathetic innervation similar to the peri-islet sympathetic innervation in the pancreas. Six weeks after transplantation prominent intra-graft, perivascular sympathetic innervation was achieved, resembling the pancreatic intra-islet, perivascular sympathetic innervation in situ. Meanwhile, in diabetic recipients, a higher graft sympathetic nerve density was found compared with grafts in normoglycemic recipients, indicating the graft neural plasticity in response to the physiological difference of the recipients and the resolving power of this imaging approach. Overall, this new graft imaging method provides a useful tool to identify the islet neurovascular complex in an ectopic environment to study islet engraftment.