Carrageenans (CGs) are hydrophilic, linear sulfated polysaccharides extracted from red algae. CGs have been utilized for tissue engineering due to their biocompatibility, and excellent physical properties. However, CGs form helical structures, which give them a gel-formation ability; hence, most CG hydrogels are thermo-reversible, ion-crosslinking methods. Because these hydrogels cannot carry heat-sensitive drugs, cells, in vivo application is limited. To solve these problems, enzymatic crosslinking method based on horseradish peroxidase (HRP)-mediated reactions with hydrogen peroxide (H2O2) was utilized to synthesize CG-based hydrogels. Gelation time was controlled from 5 sec to 5 min with various concentrations of HRP (0.005-0.025 mg/mL). It was found that the H2O2 concentration (0.005-0.035 wt%) can control the elastic modulus (150-700 Pa) of the hydrogels. In vitro 2D cell viability studies demonstrated that the ka- CGPT hydrogels had excellent bioactivity. Such injectable hydrogel platforms are promising materials and will be utilized for various tissue engineering strategies.