Macromolecule-based therapeutic agents, particularly proteins, antigens, monoclonal antibodies, transcription factors, nucleic acids, and gene editing enzymes, have the potential to offer cures for previously untreatable diseases. However, they present an enormous delivery challenge due to poor absorption and rapid metabolism in the body. Polymersomes have tremendous potential in delivering these agents to their desired intracellular location due to increased circulation times, decreased macromolecule degradation, and decreased immune responses. In this Review, we highlight the key factors in design, development, and improved performance of these vesicles for macromolecular delivery. The recent progress made toward preclinical application of these vesicles for protein and gene delivery is also covered.