In situ forming hydrogels show promise as therapeutic implants and carriers in a wide range of biomedical applications. They can easily seal or fill damaged tissue, thereby functioning as cell/drug delivery vehicles or hemostats. In this regard, strong and stable adhesion to the surrounding tissue is considered an important parameter to improve the in vivo performance of in situ forming hydrogels. In this study, tissue-adhesive gelatin-based hydrogels were prepared by dual-enzymatic cross-linking, where horseradish peroxidase (HRP) and tyrosinase (Tyr) were used. Tyr was employed to convert phenol groups of gelatin derivatives into o-quinone, which can readily react with nucleophiles (e.g., amines or thiols) on tissue surfaces, thereby resulting in strong tissue adhesion. Incorporating Tyr (0.25 kU mL⁻¹) did not affect the gelation rate or mechanical strength of HRP-cross-linked hydrogels. Importantly, the dual-enzymatically cross-linked hydrogels (GH/HRP/Tyr) exhibited significantly improved adhesive strength (34 kPa), which was superior to single HRP-cross-linked hydrogels (GH/HRP; 19 kPa) and commercially available fibrin glues (7 kPa). These dual-enzymatically cross-linked gelatin-based hydrogels with strong adhesiveness could act as promising bio-adhesives for tissue-regeneration applications.