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In the development of cell therapy products, immunocompromised animal models closer in size to humans are valuable for enhancing the translatability of in vivo findings to clinical trials. In the present study, we generated immunocompromised type 1 diabetic Göttingen mini-pig models and demonstrated the engraftment of human-induced pluripotent stem cell–derived pancreatic islet cells (iPICs). We induced hyperglycemia with a concomitant reduction in endogenous C-peptide levels in pigs that underwent thymectomy and splenectomy. After estimating the effective in vivo dose of immunosuppressants (ISs) via in vitro testing, we conducted exploratory implantation of iPICs using various implantation methods under IS treatments in one pig. Five weeks after implantation, histological analysis of the implanted iPICs embedded in fibrin gel revealed numerous islet-like structures with insulin-positive cells. Moreover, the area of the insulin-positive cells in the pre-peritoneally implanted grafts was greater than in the subcutaneously implanted grafts. Immunohistochemical analyses further revealed that these iPIC grafts contained cells positive for glucagon, somatostatin, and pancreatic polypeptides, similar to naturally occurring islets. The engraftment of iPICs was successfully reproduced. These data support the observation that the iPICs engrafted well, particularly in the pre-peritoneal space of the newly generated immunocompromised diabetic mini-pigs, forming islet-like endocrine clusters. Future evaluation of human cells in this immunocompromised pig model could accelerate and development of cell therapy products.