Pancreatic islet transplantation is a promising cell replacement therapy for patients with type 1 diabetes (T1D), an autoimmune disease that destroys insulin-producing islet β cells. However, the shortage of donor pancreatic islets significantly limits the widespread use of this strategy as a routine therapy. Pluripotent stem cell-derived insulin-producing islet organoids present a promising alternative β cell source for T1D patients. One critical challenge is the lack of vascularization in islet organoids, making it essential to investigate vascularized transplantation sites to support their survival. Brown adipose tissue (BAT) is well vascularized and secretes active cytokines, facilitating islet organoid survival. Thus, BAT represents a promising transplantation site for islet organoids, making it an ideal location to support cell replacement therapies and improve treatment approaches for T1D. Here, we describe the methods for transplanting human-induced pluripotent stem cell (iPSC)-derived islet organoids into the BAT of a mouse model.