Zwitterionic polymers and hydrogels have gained significant interest in biomedical applications due to their excellent biocompatibility and ultra-low biofouling properties. Despite this, their feasibility in cell encapsulation and in vivo cell therapy has been minimally explored. In this study, we synthesized an injectable poly (carboxybetaine acrylamide) (pCBAA) zwitterionic hydrogel tailored for cell encapsulation. Utilizing this hydrogel, we investigated its potential for in vivo extracellular vesicle (EV) therapy of breast cancer. Here, we demonstrate that low cytotoxicity, low mechanical properties, and thermal crosslinking make this injectable zwitterionic hydrogel suitable for cell encapsulation. The injectable zwitterionic hydrogel keeps encapsulated donor cells at low metabolism with reduced EV production function under the in vitro environment. In vivo hydrogel implantation indicates pCBAA hydrogel induces limited foreign body response and immune response. Moreover, the zwitterionic also promotes angiogenesis in surrounding tissue with pro-healing functions. These findings suggest the potential of zwitterionic hydrogels for cell encapsulation and cell therapy.