The development of self-healing materials with the ability to repair damage has received considerable attention. The challenge of the weak mechanical properties of host–guest (HG)-based self-healable hydrogels was largely solved by employing the β-cyclodextrin dimer (bis-CD) as a novel host cross-linker and the addition of ZnO nanoparticles (NPs). First, bis-CD, adamantane-modified alginate (ALG–Ad) and βCD-modified alginate (ALG–CD) were synthesized as the host cross-linker, guest polymer and host polymer, respectively. Then, three self-healable hydrogels, ALG–Ad/ALG–CD, ALG–Ad/bis-CD and ALG–Ad/bis-CD/ZnO, were fabricated based on HG complexation and their mechanical properties were compared with each other. According to the results, employing bis-CD instead of ALG–Ad increased the mechanical strength of the ALG–Ad/bis-CD hydrogel to 2490 Pa. The influence of the ZnO NPs on the mechanical strength of the ALG–Ad/bis-CD/ZnO nanocomposite hydrogel was also investigated by rheological measurements and the modulus was increased to 31 800 Pa by employing ZnO NPs. The ALG–Ad/bis-CD/ZnO hydrogel showed antibacterial properties due to the presence of ZnO NPs. Moreover, this nanocomposite hydrogel showed rapid self-healing behavior in less than 5 seconds, which was examined microscopically and macroscopically. The self-healing, biocompatibility and antibacterial properties of the prepared nanocomposite make it a good candidate for fabricating coatings.