Hydrogels have emerged as promising antimicrobial materials due to their unique three-dimensional structure, which provides sufficient capacity to accommodate various materials, including small molecules, polymers and particles. Coating substrates with antibacterial hydrogel layers has been recognized as an effective strategy to combat bacterial colonization. To prevent possible delamination of hydrogel coatings from substrates, it is crucial to attach hydrogel layers via stronger links, such as covalent bonds. To date, various surface chemical strategies have been developed to introduce hydrogel coatings on different substrates. In this review, we first give a brief introduction of the major strategies for designing antibacterial coatings. Then, we summarize the chemical methods used to fix the antibacterial hydrogel layer on the substrate, which include surface-initiated graft crosslinking polymerization, anchoring the hydrogel layer on the surface during crosslinking, and chemical crosslinking of layer-by-layer coating. The reaction mechanisms of each method and matched pretreatment strategies are systemically documented with the aim of introducing available protocols to researchers in related fields for designing hydrogel-coated antibacterial surfaces. Display omitted •Hydrogel coating has advantages of multipoint anchoring, uniform coverage and high loading capacity.•Antibacterial function can be designed by bacteria-repellent, contact-killing and bactericide-releasing.•Antibacterial hydrogel coating can be introduced by surface-initiated graft polymerization.•Anchoring hydrogel coating by incorporating surface functional groups into network during crosslinking.•Antibacterial hydrogel layer can be fabricated by chemical crosslinking of layer-by-layer coating.