Herein we present a tuned cell attachment on self-healable double network hydrogel bearing dynamic covalent bonds and hydrogen bonds. Agar formed first network, while glycol chitosan and oxidized carboxylmethyl cellulose formed second network in the resultant double network hydrogel. Because of the simple one-pot preparation, the hydrogel can be injected by using syringes. The moduli of the hydrogel were improved compared to that of the parent single-network. The hydrogel exhibited self-healing ability without need for heating or cut surface treatment. The incorporation of agar in the double network induced the enhanced protein adsorption, and the following cell attachments were governed by the adsorbed protein states. Therefore, the double network hydrogel holds great potential for applications in various biomedical applications.