Extrahepatic islet transplantation offers a clinically attractive alternative to intrahepatic delivery, but its success has been constrained by inadequate vascularization and lack of a supportive microenvironment. To address this, we engineered vascularized endocrine constructs (VECs) by coencapsulating pancreatic islets with human blood outgrowth endothelial cells in a good manufacturing practice-compliant amniotic membrane hydrogel (Amniogel). Amniogel provides extracellular matrix-bound prosurvival cues that enhance islet viability and function and promote endothelial self-assembly into vascular networks-improving β-cell gap junction coupling and restoring dynamic glucose-responsive insulin secretion. After subcutaneous implantation in diabetic mice, VECs anastomosed with host vessels and reestablished normoglycemia, outperforming nonvascularized controls. Furthermore, Amniogel impeded chemokine-driven cytotoxic T cell migration and delayed β-cell killing in vitro in a concentration-dependent manner. This integrative strategy, combining a scalable biological scaffold with vascularization and intrinsic barrier properties that may limit early immune cell infiltration, offers a clinically relevant path toward durable β-cell replacement therapies in type 1 diabetes.