Developing biocompatible injectable hydrogels with high mechanical strength and rapid strong tissue adhesion for hemostatic sealing of uncontrolled bleeding remains a prevailing challenge. Herein, we engineer an injectable and photo-cross-linkable hydrogel based on naturally derived gelatin methacrylate (GelMA) and N-hydroxysuccinimide-modified poly(γ-glutamic acid) (γPGA-NHS). The chemically dual-cross-linked hydrogel rapidly forms after UV light irradiation and covalently bonds to the underlying tissue to provide robust adhesion. We demonstrate a significantly improved hemostatic efficacy of the hydrogel using various injury models in rats compared to the commercially available fibrin glue. Notably, the hydrogel can achieve hemostasis in porcine liver and spleen incision, and femoral artery puncture models. Moreover, the hydrogel is used for sutureless repair of the liver defect in a rat model with a significantly suppressed inflammatory response, enhanced angiogenesis, and superior healing efficacy compared to fibrin glue. Together, this study offers a promising bioadhesive for treating severe bleeding and facilitating wound repair.