Management of diabetes mellitus relies heavily on antidiabetic agents – insulin, sulfonylureas, biguanides, and incretin-based peptides – whose conventional dosage forms are frequently limited by short plasma half-life, enzymatic degradation, poor membrane permeability, and the need for frequent dosing, all of which compromise sustained glycemic control and patient adherence. Biodegradable nanocarriers constructed from polyesters (poly(lactic-co-glycolic acid), polylactic acid, polycaprolactone) and natural biopolymers (chitosan, alginate, xanthan gum) have emerged as a mechanistically coherent strategy to overcome these limitations by protecting labile antidiabetic actives, prolonging systemic or mucosal residence, and enabling programmable, sustained drug release as the carrier undergoes hydrolytic or enzymatic biodegradation. This review comparatively examines conventional and biodegradable nanocarrier-based delivery of representative antidiabetic drugs – insulin, glibenclamide, gliclazide, glipizide, and metformin – across physicochemical, sustained-release, pharmacodynamic, and safety dimensions. Across the reviewed literature, biodegradable nanocarrier encapsulation consistently improved encapsulation efficiency, prolonged and pH-responsive drug release, and produced more stable glycemic control in preclinical models relative to conventional dosage forms. However, incomplete characterization of polymer biodegradation kinetics, nanotoxicological uncertainty, and the absence of harmonized regulatory pathways continue to constrain clinical translation. We conclude that biodegradable nanocarriers represent an empirically supported route to achieve sustained-release antidiabetic therapy, provided that standardized biodegradation characterization, robust safety evaluation, and harmonized regulatory frameworks are developed in parallel.