Extracellular vesicles (EVs) are heterogeneous membranous vesicles secreted by living cells that are involved in many physiological and pathological processes as intermediaries for intercellular communication and molecular transfer. Recent studies have shown that EVs can regulate the occurrence and development of tumors by transferring proteins, lipids and nucleic acids to immune cells as signaling molecules. As a new diagnostic biomarker and drug delivery system, EVs have broad application prospects in immunotherapy. In addition, the breakthrough of nanotechnology has promoted the development and exploration of engineered EVs for immune-targeted therapy. Herein, we review the uniqueness of EVs in immune regulation and the engineering strategies used for immunotherapy and highlight the logic of their design through typical examples. The present situation and challenges of clinical transformation are discussed, and the development prospects of EVs in immunotherapy are proposed. The goal of this review is to provide new insights into the design of immune-regulatory EVs and expand their application in cancer immunotherapy.