Beta cell replacement therapy for type 1 diabetes is hindered by poor graft survival and suboptimal function, largely due to inadequate vascularization and lack of supportive microenvironment. To address these challenges, we developed a clinically scalable, extracellular matrix (ECM)–mimetic hydrogel, termed Amniogel, derived from human amniotic membrane via streamlined, clinically compliant process. Co-encapsulation of pancreatic islets with blood outgrowth endothelial cells (BOECs) within Amniogel facilitated the formation of prevascularized endocrine constructs (VECs).